C2S for Red Hat Enterprise Linux 6


CCE ID Rule Title Description Rationale Variable Setting NIST 800-53 Mapping
CCE-27283-1 Set Account Expiration Following Inactivity To specify the number of days after a password expires (which signifies inactivity) until an account is permanently disabled, add or correct the following lines in /etc/default/useradd, substituting NUM_DAYS appropriately:
INACTIVE=
A value of 35 is recommended; however, this profile expects that the value is set to . If a password is currently on the verge of expiration, then 35 days remain until the account is automatically disabled. However, if the password will not expire for another 60 days, then 95 days could elapse until the account would be automatically disabled. See the useradd man page for more information. Determining the inactivity timeout must be done with careful consideration of the length of a "normal" period of inactivity for users in the particular environment. Setting the timeout too low incurs support costs and also has the potential to impact availability of the system to legitimate users.
Disabling inactive accounts ensures that accounts which may not have been responsibly removed are not available to attackers who may have compromised their credentials. IA-4(e)
AC-2(3)
CM-6(a)
CCE-27609-7 Ensure All Accounts on the System Have Unique Names Ensure accounts on the system have unique names. To ensure all accounts have unique names, run the following command:
$ sudo getent passwd | awk -F: '{ print $1}' | uniq -d
If a username is returned, change or delete the username.
Unique usernames allow for accountability on the system.
CCE-26985-2 Set Password Maximum Age To specify password maximum age for new accounts, edit the file /etc/login.defs and add or correct the following line:
PASS_MAX_DAYS 
A value of 180 days is sufficient for many environments. The DoD requirement is 60. The profile requirement is .
Any password, no matter how complex, can eventually be cracked. Therefore, passwords need to be changed periodically. If the operating system does not limit the lifetime of passwords and force users to change their passwords, there is the risk that the operating system passwords could be compromised.

Setting the password maximum age ensures users are required to periodically change their passwords. Requiring shorter password lifetimes increases the risk of users writing down the password in a convenient location subject to physical compromise.
IA-5(f)
IA-5(1)(d)
CM-6(a)
CCE-27013-2 Set Password Minimum Age To specify password minimum age for new accounts, edit the file /etc/login.defs and add or correct the following line:
PASS_MIN_DAYS 
A value of 1 day is considered sufficient for many environments. The DoD requirement is 1. The profile requirement is .
Enforcing a minimum password lifetime helps to prevent repeated password changes to defeat the password reuse or history enforcement requirement. If users are allowed to immediately and continually change their password, then the password could be repeatedly changed in a short period of time to defeat the organization's policy regarding password reuse.

Setting the minimum password age protects against users cycling back to a favorite password after satisfying the password reuse requirement.
IA-5(f)
IA-5(1)(d)
CM-6(a)
CCE-26971-2 Verify Only Root Has UID 0 If any account other than root has a UID of 0, this misconfiguration should be investigated and the accounts other than root should be removed or have their UID changed.
If the account is associated with system commands or applications the UID should be changed to one greater than "0" but less than "1000." Otherwise assign a UID greater than "1000" that has not already been assigned.
An account has root authority if it has a UID of 0. Multiple accounts with a UID of 0 afford more opportunity for potential intruders to guess a password for a privileged account. Proper configuration of sudo is recommended to afford multiple system administrators access to root privileges in an accountable manner. IA-2
AC-6(5)
IA-4(b)
CCE-26741-9 Limit Password Reuse Do not allow users to reuse recent passwords. This can be accomplished by using the remember option for the pam_unix or pam_pwhistory PAM modules.

In the file /etc/pam.d/system-auth, append remember= to the line which refers to the pam_unix.so or pam_pwhistory.somodule, as shown below:
  • for the pam_unix.so case:
    password sufficient pam_unix.so ...existing_options... remember=
  • for the pam_pwhistory.so case:
    password requisite pam_pwhistory.so ...existing_options... remember=
The DoD STIG requirement is 5 passwords.
Preventing re-use of previous passwords helps ensure that a compromised password is not re-used by a user. IA-5(f)
IA-5(1)(e)
CCE-26988-6 Set Password Warning Age To specify how many days prior to password expiration that a warning will be issued to users, edit the file /etc/login.defs and add or correct the following line:
PASS_WARN_AGE 
The DoD requirement is 7. The profile requirement is .
Setting the password warning age enables users to make the change at a practical time. IA-5(f)
IA-5(1)(d)
CM-6(a)
CCE-26844-1 Set Deny For Failed Password Attempts To configure the system to lock out accounts after a number of incorrect login attempts using pam_faillock.so, modify the content of both /etc/pam.d/system-auth and /etc/pam.d/password-auth as follows:

  • add the following line immediately before the pam_unix.so statement in the AUTH section:
    auth required pam_faillock.so preauth silent deny= unlock_time= fail_interval=
  • add the following line immediately after the pam_unix.so statement in the AUTH section:
    auth [default=die] pam_faillock.so authfail deny= unlock_time= fail_interval=
  • add the following line immediately before the pam_unix.so statement in the ACCOUNT section:
    account required pam_faillock.so
Locking out user accounts after a number of incorrect attempts prevents direct password guessing attacks. CM-6(a)
AC-7(a)
CCE-26917-5 Ensure the Default Bash Umask is Set Correctly To ensure the default umask for users of the Bash shell is set properly, add or correct the umask setting in /etc/bashrc to read as follows:
umask 
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users. AC-6(1)
CM-6(a)
CCE-26669-2 Ensure the Default Umask is Set Correctly in /etc/profile To ensure the default umask controlled by /etc/profile is set properly, add or correct the umask setting in /etc/profile to read as follows:
umask 
The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users. AC-6(1)
CM-6(a)
CCE-27135-3 Build and Test AIDE Database Run the following command to generate a new database:
$ sudo /usr/sbin/aide --init
By default, the database will be written to the file /var/lib/aide/aide.db.new.gz. Storing the database, the configuration file /etc/aide.conf, and the binary /usr/sbin/aide (or hashes of these files), in a secure location (such as on read-only media) provides additional assurance about their integrity. The newly-generated database can be installed as follows:
$ sudo cp /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz
To initiate a manual check, run the following command:
$ sudo /usr/sbin/aide --check
If this check produces any unexpected output, investigate.
For AIDE to be effective, an initial database of "known-good" information about files must be captured and it should be able to be verified against the installed files. CM-6(a)
CCE-27222-9 Configure Periodic Execution of AIDE At a minimum, AIDE should be configured to run a weekly scan. To implement a daily execution of AIDE at 4:05am using cron, add the following line to /etc/crontab:
05 4 * * * root /usr/sbin/aide --check
To implement a weekly execution of AIDE at 4:05am using cron, add the following line to /etc/crontab:
05 4 * * 0 root /usr/sbin/aide --check
AIDE can be executed periodically through other means; this is merely one example. The usage of cron's special time codes, such as @daily and @weekly is acceptable.
By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

Unauthorized changes to the baseline configuration could make the system vulnerable to various attacks or allow unauthorized access to the operating system. Changes to operating system configurations can have unintended side effects, some of which may be relevant to security.

Detecting such changes and providing an automated response can help avoid unintended, negative consequences that could ultimately affect the security state of the operating system. The operating system's Information Management Officer (IMO)/Information System Security Officer (ISSO) and System Administrators (SAs) must be notified via email and/or monitoring system trap when there is an unauthorized modification of a configuration item.
SI-7
SI-7(1)
CM-6(a)
CCE-26651-0 Ensure auditd Collects File Deletion Events by User At a minimum the audit system should collect file deletion events for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename,renameat -F auid>=500 -F auid!=unset -F key=delete
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir,unlink,unlinkat,rename -S renameat -F auid>=500 -F auid!=unset -F key=delete
Auditing file deletions will create an audit trail for files that are removed from the system. The audit trail could aid in system troubleshooting, as well as, detecting malicious processes that attempt to delete log files to conceal their presence. AC-3(10)
CCE-26612-2 Make the auditd Configuration Immutable If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d in order to make the auditd configuration immutable:
-e 2
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file in order to make the auditd configuration immutable:
-e 2
With this setting, a reboot will be required to change any audit rules.
Making the audit configuration immutable prevents accidental as well as malicious modification of the audit rules, although it may be problematic if legitimate changes are needed during system operation AC-6(9)
CM-6(a)
CCE-26611-4 Ensure auditd Collects Information on Kernel Module Loading and Unloading To capture kernel module loading and unloading events, use following lines, setting ARCH to either b32 for 32-bit system, or having two lines for both b32 and b64 in case your system is 64-bit:

-a always,exit -F arch=ARCH -S init_module,delete_module -F key=modules

The place to add the lines depends on a way auditd daemon is configured. If it is configured to use the augenrules program (the default), add the lines to a file with suffix .rules in the directory /etc/audit/rules.d. If the auditd daemon is configured to use the auditctl utility, add the lines to file /etc/audit/audit.rules.
The addition/removal of kernel modules can be used to alter the behavior of the kernel and potentially introduce malicious code into kernel space. It is important to have an audit trail of modules that have been introduced into the kernel. AC-3(10)
CCE-26691-6 Record Attempts to Alter Logon and Logout Events The audit system already collects login information for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d in order to watch for attempted manual edits of files involved in storing logon events:
-w /var/log/tallylog -p wa -k logins
-w /var/run/faillock -p wa -k logins
-w /var/log/lastlog -p wa -k logins
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file in order to watch for unattempted manual edits of files involved in storing logon events:
-w /var/log/tallylog -p wa -k logins
-w /var/run/faillock -p wa -k logins
-w /var/log/lastlog -p wa -k logins
Manual editing of these files may indicate nefarious activity, such as an attacker attempting to remove evidence of an intrusion. AC-3(10)
CCE-26657-7 Record Events that Modify the System's Mandatory Access Controls If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-w /etc/selinux/ -p wa -k MAC-policy
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-w /etc/selinux/ -p wa -k MAC-policy
The system's mandatory access policy (SELinux) should not be arbitrarily changed by anything other than administrator action. All changes to MAC policy should be audited. AC-3(10)
CCE-26573-6 Ensure auditd Collects Information on Exporting to Media (successful) At a minimum, the audit system should collect media exportation events for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S mount -F auid>=500 -F auid!=unset -F key=export
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S mount -F auid>=500 -F auid!=unset -F key=export
The unauthorized exportation of data to external media could result in an information leak where classified information, Privacy Act information, and intellectual property could be lost. An audit trail should be created each time a filesystem is mounted to help identify and guard against information loss. AC-3(10)
CCE-26648-6 Record Events that Modify the System's Network Environment If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S sethostname,setdomainname -F key=audit_rules_networkconfig_modification
-w /etc/issue -p wa -k audit_rules_networkconfig_modification
-w /etc/issue.net -p wa -k audit_rules_networkconfig_modification
-w /etc/hosts -p wa -k audit_rules_networkconfig_modification
-w /etc/sysconfig/network -p wa -k audit_rules_networkconfig_modification
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S sethostname,setdomainname -F key=audit_rules_networkconfig_modification
-w /etc/issue -p wa -k audit_rules_networkconfig_modification
-w /etc/issue.net -p wa -k audit_rules_networkconfig_modification
-w /etc/hosts -p wa -k audit_rules_networkconfig_modification
-w /etc/sysconfig/network -p wa -k audit_rules_networkconfig_modification
The network environment should not be modified by anything other than administrator action. Any change to network parameters should be audited. AC-3(10)
CCE-26457-2 Ensure auditd Collects Information on the Use of Privileged Commands At a minimum, the audit system should collect the execution of privileged commands for all users and root. To find the relevant setuid / setgid programs, run the following command for each local partition PART:
$ sudo find PART -xdev -type f -perm -4000 -o -type f -perm -2000 2>/dev/null
If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add a line of the following form to a file with suffix .rules in the directory /etc/audit/rules.d for each setuid / setgid program on the system, replacing the SETUID_PROG_PATH part with the full path of that setuid / setgid program in the list:
-a always,exit -F path=SETUID_PROG_PATH -F perm=x -F auid>=500 -F auid!=unset -F key=special-config-changes
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add a line of the following form to /etc/audit/audit.rules for each setuid / setgid program on the system, replacing the SETUID_PROG_PATH part with the full path of that setuid / setgid program in the list:
-a always,exit -F path=SETUID_PROG_PATH -F perm=x -F auid>=500 -F auid!=unset -F key=special-config-changes
Misuse of privileged functions, either intentionally or unintentionally by authorized users, or by unauthorized external entities that have compromised system accounts, is a serious and ongoing concern and can have significant adverse impacts on organizations. Auditing the use of privileged functions is one way to detect such misuse and identify the risk from insider and advanced persistent threast.

Privileged programs are subject to escalation-of-privilege attacks, which attempt to subvert their normal role of providing some necessary but limited capability. As such, motivation exists to monitor these programs for unusual activity.
AC-3(10)
CCE-26610-6 Record Attempts to Alter Process and Session Initiation Information The audit system already collects process information for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d in order to watch for attempted manual edits of files involved in storing such process information:
-w /var/run/utmp -p wa -k session
-w /var/log/btmp -p wa -k session
-w /var/log/wtmp -p wa -k session
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file in order to watch for attempted manual edits of files involved in storing such process information:
-w /var/run/utmp -p wa -k session
-w /var/log/btmp -p wa -k session
-w /var/log/wtmp -p wa -k session
Manual editing of these files may indicate nefarious activity, such as an attacker attempting to remove evidence of an intrusion. AC-3(10)
CCE-26662-7 Ensure auditd Collects System Administrator Actions At a minimum, the audit system should collect administrator actions for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-w /etc/sudoers -p wa -k actions
-w /etc/sudoers.d/ -p wa -k actions
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-w /etc/sudoers -p wa -k actions
-w /etc/sudoers.d/ -p wa -k actions
The actions taken by system administrators should be audited to keep a record of what was executed on the system, as well as, for accountability purposes. AC-3(10)
CCE-26242-8 Record attempts to alter time through adjtimex If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S adjtimex -F key=audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S adjtimex -F key=audit_time_rules
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S adjtimex -F key=audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S adjtimex -F key=audit_time_rules
The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport. Multiple system calls can be defined on the same line to save space if desired, but is not required. See an example of multiple combined syscalls:
-a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=audit_time_rules
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited. AC-3(10)
CCE-27203-9 Record attempts to alter time through settimeofday If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S settimeofday -F key=audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S settimeofday -F key=audit_time_rules
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S settimeofday -F key=audit_time_rules
If the system is 64 bit then also add the following line:
-a always,exit -F arch=b64 -S settimeofday -F key=audit_time_rules
The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport. Multiple system calls can be defined on the same line to save space if desired, but is not required. See an example of multiple combined syscalls:
-a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=audit_time_rules
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited. AC-3(10)
CCE-27169-2 Record Attempts to Alter Time Through stime If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d for both 32 bit and 64 bit systems:
-a always,exit -F arch=b32 -S stime -F key=audit_time_rules
Since the 64 bit version of the "stime" system call is not defined in the audit lookup table, the corresponding "-F arch=b64" form of this rule is not expected to be defined on 64 bit systems (the aforementioned "-F arch=b32" stime rule form itself is sufficient for both 32 bit and 64 bit systems). If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file for both 32 bit and 64 bit systems:
-a always,exit -F arch=b32 -S stime -F key=audit_time_rules
Since the 64 bit version of the "stime" system call is not defined in the audit lookup table, the corresponding "-F arch=b64" form of this rule is not expected to be defined on 64 bit systems (the aforementioned "-F arch=b32" stime rule form itself is sufficient for both 32 bit and 64 bit systems). The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport. Multiple system calls can be defined on the same line to save space if desired, but is not required. See an example of multiple combined system calls:
-a always,exit -F arch=b64 -S adjtimex,settimeofday -F key=audit_time_rules
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited. AC-3(10)
CCE-27172-6 Record Attempts to Alter the localtime File If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following line to a file with suffix .rules in the directory /etc/audit/rules.d:
-w /etc/localtime -p wa -k audit_time_rules
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following line to /etc/audit/audit.rules file:
-w /etc/localtime -p wa -k audit_time_rules
The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport and should always be used.
Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited. AC-3(10)
AU-12(c)
CCE-26712-0 Ensure auditd Collects Unauthorized Access Attempts to Files (unsuccessful) At a minimum the audit system should collect unauthorized file accesses for all users and root. If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d:
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=500 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=500 -F auid!=unset -F key=access
If the system is 64 bit then also add the following lines:
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=500 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=500 -F auid!=unset -F key=access
If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file:
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=500 -F auid!=unset -F key=access
-a always,exit -F arch=b32 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=500 -F auid!=unset -F key=access
If the system is 64 bit then also add the following lines:
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EACCES -F auid>=500 -F auid!=unset -F key=access
-a always,exit -F arch=b64 -S creat,open,openat,open_by_handle_at,truncate,ftruncate -F exit=-EPERM -F auid>=500 -F auid!=unset -F key=access
Unsuccessful attempts to access files could be an indicator of malicious activity on a system. Auditing these events could serve as evidence of potential system compromise. AC-3(10)
CCE-26664-3 Record Events that Modify User/Group Information If the auditd daemon is configured to use the augenrules program to read audit rules during daemon startup (the default), add the following lines to a file with suffix .rules in the directory /etc/audit/rules.d, in order to capture events that modify account changes:
-w /etc/group -p wa -k audit_rules_usergroup_modification
-w /etc/passwd -p wa -k audit_rules_usergroup_modification
-w /etc/gshadow -p wa -k audit_rules_usergroup_modification
-w /etc/shadow -p wa -k audit_rules_usergroup_modification
-w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification

If the auditd daemon is configured to use the auditctl utility to read audit rules during daemon startup, add the following lines to /etc/audit/audit.rules file, in order to capture events that modify account changes:
-w /etc/group -p wa -k audit_rules_usergroup_modification
-w /etc/passwd -p wa -k audit_rules_usergroup_modification
-w /etc/gshadow -p wa -k audit_rules_usergroup_modification
-w /etc/shadow -p wa -k audit_rules_usergroup_modification
-w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification
In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy. AC-3(10)
CCE-27241-9 Configure auditd mail_acct Action on Low Disk Space The auditd service can be configured to send email to a designated account in certain situations. Add or correct the following line in /etc/audit/auditd.conf to ensure that administrators are notified via email for those situations:
action_mail_acct = 
Email sent to the root account is typically aliased to the administrators of the system, who can take appropriate action. IA-5(1)
AU-5(a)
AU-5(2)
CM-6(a)
CCE-27239-3 Configure auditd admin_space_left Action on Low Disk Space The auditd service can be configured to take an action when disk space is running low but prior to running out of space completely. Edit the file /etc/audit/auditd.conf. Add or modify the following line, substituting ACTION appropriately:
admin_space_left_action = ACTION
Set this value to single to cause the system to switch to single user mode for corrective action. Acceptable values also include suspend and halt. For certain systems, the need for availability outweighs the need to log all actions, and a different setting should be determined. Details regarding all possible values for ACTION are described in the auditd.conf man page.
Administrators should be made aware of an inability to record audit records. If a separate partition or logical volume of adequate size is used, running low on space for audit records should never occur. AU-5(b)
AU-5(2)
AU-5(1)
AU-5(4)
CM-6(a)
CCE-27550-3 Configure auditd Max Log File Size Determine the amount of audit data (in megabytes) which should be retained in each log file. Edit the file /etc/audit/auditd.conf. Add or modify the following line, substituting the correct value of for STOREMB:
max_log_file = STOREMB
Set the value to 6 (MB) or higher for general-purpose systems. Larger values, of course, support retention of even more audit data.
The total storage for audit log files must be large enough to retain log information over the period required. This is a function of the maximum log file size and the number of logs retained. AU-11
CM-6(a)
CCE-27237-7 Configure auditd max_log_file_action Upon Reaching Maximum Log Size The default action to take when the logs reach their maximum size is to rotate the log files, discarding the oldest one. To configure the action taken by auditd, add or correct the line in /etc/audit/auditd.conf:
max_log_file_action = ACTION
Possible values for ACTION are described in the auditd.conf man page. These include:
  • syslog
  • suspend
  • rotate
  • keep_logs
Set the ACTION to rotate to ensure log rotation occurs. This is the default. The setting is case-insensitive.
Automatically rotating logs (by setting this to rotate) minimizes the chances of the system unexpectedly running out of disk space by being overwhelmed with log data. However, for systems that must never discard log data, or which use external processes to transfer it and reclaim space, keep_logs can be employed. AU-5(b)
AU-5(2)
AU-5(1)
AU-5(4)
CM-6(a)
CCE-27238-5 Configure auditd space_left Action on Low Disk Space The auditd service can be configured to take an action when disk space starts to run low. Edit the file /etc/audit/auditd.conf. Modify the following line, substituting ACTION appropriately:
space_left_action = ACTION
Possible values for ACTION are described in the auditd.conf man page. These include:
  • syslog
  • email
  • exec
  • suspend
  • single
  • halt
Set this to email (instead of the default, which is suspend) as it is more likely to get prompt attention. Acceptable values also include suspend, single, and halt.
Notifying administrators of an impending disk space problem may allow them to take corrective action prior to any disruption. AU-5(b)
AU-5(2)
AU-5(1)
AU-5(4)
CM-6(a)
CCE-26974-6 Modify the System Login Banner To configure the system login banner edit /etc/issue. Replace the default text with a message compliant with the local site policy or a legal disclaimer. The DoD required text is either:

You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls) to protect USG interests -- not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.


OR:

I've read & consent to terms in IS user agreem't.
Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.

System use notifications are required only for access via login interfaces with human users and are not required when such human interfaces do not exist.
AC-8(c)
CCE-26840-9 Verify that All World-Writable Directories Have Sticky Bits Set When the so-called 'sticky bit' is set on a directory, only the owner of a given file may remove that file from the directory. Without the sticky bit, any user with write access to a directory may remove any file in the directory. Setting the sticky bit prevents users from removing each other's files. In cases where there is no reason for a directory to be world-writable, a better solution is to remove that permission rather than to set the sticky bit. However, if a directory is used by a particular application, consult that application's documentation instead of blindly changing modes.
To set the sticky bit on a world-writable directory DIR, run the following command:
$ sudo chmod +t DIR
Failing to set the sticky bit on public directories allows unauthorized users to delete files in the directory structure.

The only authorized public directories are those temporary directories supplied with the system, or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system, by users for temporary file storage (such as /tmp), and for directories requiring global read/write access.
CM-6(a)
AC-6(1)
CCE-27091-8 Disable Host-Based Authentication SSH's cryptographic host-based authentication is more secure than .rhosts authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organization.

To disable host-based authentication, add or correct the following line in /etc/ssh/sshd_config:
HostbasedAuthentication no
SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts. AC-3
AC-17(a)
CM-7(a)
CM-7(b)
CM-6(a)
CCE-27221-1 Disable Prelinking The prelinking feature changes binaries in an attempt to decrease their startup time. In order to disable it, change or add the following line inside the file /etc/sysconfig/prelink:
PRELINKING=no
Next, run the following command to return binaries to a normal, non-prelinked state:
$ sudo /usr/sbin/prelink -ua
Because the prelinking feature changes binaries, it can interfere with the operation of certain software and/or modes such as AIDE, FIPS, etc. SC-13
CM-6(a)
CCE-27033-0 Disable Core Dumps for All Users To disable core dumps for all users, add the following line to /etc/security/limits.conf, or to a file within the /etc/security/limits.d/ directory:
*     hard   core    0
A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.
CCE-26709-6 Ensure gpgcheck Enabled In Main yum Configuration The gpgcheck option controls whether RPM packages' signatures are always checked prior to installation. To configure yum to check package signatures before installing them, ensure the following line appears in /etc/yum.conf in the [main] section:
gpgcheck=1
Changes to any software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor.
Accordingly, patches, service packs, device drivers, or operating system components must be signed with a certificate recognized and approved by the organization.
Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA).
CM-5(3)
SI-7
SC-12
SC-12(3)
CM-6(a)
SA-12
SA-12(10)
CM-11(a)
CM-11(b)
CCE-26647-8 Ensure gpgcheck Enabled for All yum Package Repositories To ensure signature checking is not disabled for any repos, remove any lines from files in /etc/yum.repos.d of the form:
gpgcheck=0
Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This ensures the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. Certificates used to verify the software must be from an approved Certificate Authority (CA)." CM-5(3)
SI-7
SC-12
SC-12(3)
CM-6(a)
SA-12
SA-12(10)
CM-11(a)
CM-11(b)
CCE-27014-0 Ensure Logrotate Runs Periodically The logrotate utility allows for the automatic rotation of log files. The frequency of rotation is specified in /etc/logrotate.conf, which triggers a cron task. To configure logrotate to run daily, add or correct the following line in /etc/logrotate.conf:
# rotate log files frequency
daily
Log files that are not properly rotated run the risk of growing so large that they fill up the /var/log partition. Valuable logging information could be lost if the /var/log partition becomes full. CM-6(a)
CCE-26506-6 Ensure Red Hat GPG Key Installed To ensure the system can cryptographically verify base software packages come from Red Hat (and to connect to the Red Hat Network to receive them), the Red Hat GPG key must properly be installed. To install the Red Hat GPG key, run:
$ sudo subscription-manager register
If the system is not connected to the Internet or an RHN Satellite, then install the Red Hat GPG key from trusted media such as the Red Hat installation CD-ROM or DVD. Assuming the disc is mounted in /media/cdrom, use the following command as the root user to import it into the keyring:
$ sudo rpm --import /media/cdrom/RPM-GPG-KEY
Alternatively, the key may be pre-loaded during the RHEL installation. In such cases, the key can be installed by running the following command:
sudo rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
Changes to software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor. The Red Hat GPG key is necessary to cryptographically verify packages are from Red Hat. CM-5(3)
SI-7
SC-12
SC-12(3)
CM-6(a)
CCE-82264-3 Verify Group Who Owns cron.d To properly set the group owner of /etc/cron.d, run the command:
$ sudo chgrp root /etc/cron.d
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82231-2 Verify Group Who Owns cron.daily To properly set the group owner of /etc/cron.daily, run the command:
$ sudo chgrp root /etc/cron.daily
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82210-6 Verify Group Who Owns cron.hourly To properly set the group owner of /etc/cron.hourly, run the command:
$ sudo chgrp root /etc/cron.hourly
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82254-4 Verify Group Who Owns cron.monthly To properly set the group owner of /etc/cron.monthly, run the command:
$ sudo chgrp root /etc/cron.monthly
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82241-1 Verify Group Who Owns cron.weekly To properly set the group owner of /etc/cron.weekly, run the command:
$ sudo chgrp root /etc/cron.weekly
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82221-3 Verify Group Who Owns Crontab To properly set the group owner of /etc/crontab, run the command:
$ sudo chgrp root /etc/crontab
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-26930-8 Verify Group Who Owns group File To properly set the group owner of /etc/group, run the command:
$ sudo chgrp root /etc/group
The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security. CM-6(a)
AC-6(1)
CCE-26975-3 Verify Group Who Owns gshadow File To properly set the group owner of /etc/gshadow, run the command:
$ sudo chgrp root /etc/gshadow
The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security. CM-6(a)
AC-6(1)
CCE-26856-5 Verify Group Who Owns passwd File To properly set the group owner of /etc/passwd, run the command:
$ sudo chgrp root /etc/passwd
The /etc/passwd file contains information about the users that are configured on the system. Protection of this file is critical for system security. CM-6(a)
AC-6(1)
CCE-26967-0 Verify Group Who Owns shadow File To properly set the group owner of /etc/shadow, run the command:
$ sudo chgrp root /etc/shadow
The /etc/shadow file stores password hashes. Protection of this file is critical for system security. CM-6(a)
AC-6(1)
CCE-27022-3 Verify /etc/grub.conf Group Ownership The file /etc/grub.conf should be group-owned by the root group to prevent destruction or modification of the file. To properly set the group owner of /etc/grub.conf, run the command:
$ sudo chgrp root /etc/grub.conf
The root group is a highly-privileged group. Furthermore, the group-owner of this file should not have any access privileges anyway. CM-6(a)
AC-6(1)
CCE-82903-6 Verify Group Who Owns SSH Server config file To properly set the group owner of /etc/ssh/sshd_config, run the command:
$ sudo chgrp root /etc/ssh/sshd_config
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. AC-17(a)
CM-6(a)
AC-6(1)
CCE-82269-2 Verify Owner on cron.d To properly set the owner of /etc/cron.d, run the command:
$ sudo chown root /etc/cron.d 
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82235-3 Verify Owner on cron.daily To properly set the owner of /etc/cron.daily, run the command:
$ sudo chown root /etc/cron.daily 
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82207-2 Verify Owner on cron.hourly To properly set the owner of /etc/cron.hourly, run the command:
$ sudo chown root /etc/cron.hourly 
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82257-7 Verify Owner on cron.monthly To properly set the owner of /etc/cron.monthly, run the command:
$ sudo chown root /etc/cron.monthly 
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82245-2 Verify Owner on cron.weekly To properly set the owner of /etc/cron.weekly, run the command:
$ sudo chown root /etc/cron.weekly 
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82216-3 Verify Owner on crontab To properly set the owner of /etc/crontab, run the command:
$ sudo chown root /etc/crontab 
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-26822-7 Verify User Who Owns group File To properly set the owner of /etc/group, run the command:
$ sudo chown root /etc/group 
The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security. CM-6(a)
AC-6(1)
CCE-27026-4 Verify User Who Owns gshadow File To properly set the owner of /etc/gshadow, run the command:
$ sudo chown root /etc/gshadow 
The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security. CM-6(a)
AC-6(1)
CCE-26953-0 Verify User Who Owns passwd File To properly set the owner of /etc/passwd, run the command:
$ sudo chown root /etc/passwd 
The /etc/passwd file contains information about the users that are configured on the system. Protection of this file is critical for system security. CM-6(a)
AC-6(1)
CCE-26947-2 Verify User Who Owns shadow File To properly set the owner of /etc/shadow, run the command:
$ sudo chown root /etc/shadow 
The /etc/shadow file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture. CM-6(a)
AC-6(1)
CCE-26995-1 Verify /etc/grub.conf User Ownership The file /etc/grub.conf should be owned by the root user to prevent destruction or modification of the file. To properly set the owner of /etc/grub.conf, run the command:
$ sudo chown root /etc/grub.conf 
Only root should be able to modify important boot parameters. CM-6(a)
AC-6(1)
CCE-82900-2 Verify Owner on SSH Server config file To properly set the owner of /etc/ssh/sshd_config, run the command:
$ sudo chown root /etc/ssh/sshd_config 
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. AC-17(a)
CM-6(a)
AC-6(1)
CCE-27289-8 Verify that System Executables Have Restrictive Permissions System executables are stored in the following directories by default:
/bin
/sbin
/usr/bin
/usr/libexec
/usr/local/bin
/usr/local/sbin
/usr/sbin
All files in these directories should not be group-writable or world-writable. If any file FILE in these directories is found to be group-writable or world-writable, correct its permission with the following command:
$ sudo chmod go-w FILE
System binaries are executed by privileged users, as well as system services, and restrictive permissions are necessary to ensure execution of these programs cannot be co-opted. CM-6(a)
AC-6(1)
CCE-82275-9 Verify Permissions on cron.d To properly set the permissions of /etc/cron.d, run the command:
$ sudo chmod 0700 /etc/cron.d
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82238-7 Verify Permissions on cron.daily To properly set the permissions of /etc/cron.daily, run the command:
$ sudo chmod 0700 /etc/cron.daily
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82228-8 Verify Permissions on cron.hourly To properly set the permissions of /etc/cron.hourly, run the command:
$ sudo chmod 0700 /etc/cron.hourly
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82261-9 Verify Permissions on cron.monthly To properly set the permissions of /etc/cron.monthly, run the command:
$ sudo chmod 0700 /etc/cron.monthly
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82248-6 Verify Permissions on cron.weekly To properly set the permissions of /etc/cron.weekly, run the command:
$ sudo chmod 0700 /etc/cron.weekly
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-82204-9 Verify Permissions on crontab To properly set the permissions of /etc/crontab, run the command:
$ sudo chmod 0600 /etc/crontab
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes. CM-6(a)
AC-6(1)
CCE-26954-8 Verify Permissions on group File To properly set the permissions of /etc/passwd, run the command:
$ sudo chmod 0644 /etc/passwd
The /etc/group file contains information regarding groups that are configured on the system. Protection of this file is important for system security. CM-6(a)
AC-6(1)
CCE-26951-4 Verify Permissions on gshadow File To properly set the permissions of /etc/gshadow, run the command:
$ sudo chmod 0000 /etc/gshadow
The /etc/gshadow file contains group password hashes. Protection of this file is critical for system security. CM-6(a)
AC-6(1)
CCE-26868-0 Verify Permissions on passwd File To properly set the permissions of /etc/passwd, run the command:
$ sudo chmod 0644 /etc/passwd
If the /etc/passwd file is writable by a group-owner or the world the risk of its compromise is increased. The file contains the list of accounts on the system and associated information, and protection of this file is critical for system security. CM-6(a)
AC-6(1)
CCE-26992-8 Verify Permissions on shadow File To properly set the permissions of /etc/shadow, run the command:
$ sudo chmod 0000 /etc/shadow
The /etc/shadow file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture. CM-6(a)
AC-6(1)
CCE-26949-8 Verify /boot/grub/grub.conf Permissions File permissions for /boot/grub/grub.conf should be set to 600, which is the default. To properly set the permissions of /boot/grub/grub.conf, run the command:
$ sudo chmod 600 /boot/grub/grub.conf
Proper permissions ensure that only the root user can modify important boot parameters. CM-6(a)
AC-6(1)
CCE-26981-1 Ensure that User Home Directories are not Group-Writable or World-Readable For each human user of the system, view the permissions of the user's home directory:
# ls -ld /home/USER
Ensure that the directory is not group-writable and that it is not world-readable. If necessary, repair the permissions:
# chmod g-w /home/USER
# chmod o-rwx /home/USER
User home directories contain many configuration files which affect the behavior of a user's account. No user should ever have write permission to another user's home directory. Group shared directories can be configured in sub-directories or elsewhere in the filesystem if they are needed. Typically, user home directories should not be world-readable, as it would disclose file names to other users. If a subset of users need read access to one another's home directories, this can be provided using groups or ACLs. CM-6(a)
AC-6(1)
CM-6(a)
CCE-82896-2 Verify Permissions on SSH Server config file To properly set the permissions of /etc/ssh/sshd_config, run the command:
$ sudo chmod 0600 /etc/ssh/sshd_config
Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes. AC-17(a)
CM-6(a)
AC-6(1)
CCE-26769-0 Ensure All SGID Executables Are Authorized The SGID (set group id) bit should be set only on files that were installed via authorized means. A straightforward means of identifying unauthorized SGID files is determine if any were not installed as part of an RPM package, which is cryptographically verified. Investigate the origin of any unpackaged SGID files. This configuration check considers authorized SGID files which were installed via RPM. It is assumed that when an individual has sudo access to install an RPM and all packages are signed with an organizationally-recognized GPG key, the software should be considered an approved package on the system. Any SGID file not deployed through an RPM will be flagged for further review. Executable files with the SGID permission run with the privileges of the owner of the file. SGID files of uncertain provenance could allow for unprivileged users to elevate privileges. The presence of these files should be strictly controlled on the system. CM-6(a)
AC-6(1)
CCE-26497-8 Ensure All SUID Executables Are Authorized The SUID (set user id) bit should be set only on files that were installed via authorized means. A straightforward means of identifying unauthorized SUID files is determine if any were not installed as part of an RPM package, which is cryptographically verified. Investigate the origin of any unpackaged SUID files. This configuration check considers authorized SUID files which were installed via RPM. It is assumed that when an individual has sudo access to install an RPM and all packages are signed with an organizationally-recognized GPG key, the software should be considered an approved package on the system. Any SUID file not deployed through an RPM will be flagged for further review. Executable files with the SUID permission run with the privileges of the owner of the file. SUID files of uncertain provenance could allow for unprivileged users to elevate privileges. The presence of these files should be strictly controlled on the system. CM-6(a)
AC-6(1)
CCE-26910-0 Ensure No World-Writable Files Exist It is generally a good idea to remove global (other) write access to a file when it is discovered. However, check with documentation for specific applications before making changes. Also, monitor for recurring world-writable files, as these may be symptoms of a misconfigured application or user account. Finally, this applies to real files and not virtual files that are a part of pseudo file systems such as sysfs or procfs. Data in world-writable files can be modified by any user on the system. In almost all circumstances, files can be configured using a combination of user and group permissions to support whatever legitimate access is needed without the risk caused by world-writable files. CM-6(a)
AC-6(1)
CCE-26872-2 Ensure All Files Are Owned by a Group If any files are not owned by a group, then the cause of their lack of group-ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate group. Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed. CM-6(a)
AC-6(1)
CCE-27195-7 Enable GUI Warning Banner To enable displaying a login warning banner in the GNOME Display Manager's login screen, run the following command:
$ sudo gconftool-2 --direct \
  --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
  --type bool \
  --set /apps/gdm/simple-greeter/banner_message_enable true
To display a banner, this setting must be enabled and then banner text must also be set.
An appropriate warning message reinforces policy awareness during the login process and facilitates possible legal action against attackers. AC-8(a)
AC-8(b)
AC-8(c)
CCE-27017-3 Set GUI Warning Banner Text To set the text shown by the GNOME Display Manager in the login screen, run the following command:
$ sudo gconftool-2 --direct \
  --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
  --type string \
  --set /apps/gdm/simple-greeter/banner_message_text \
  "Text of the warning banner here"
When entering a warning banner that spans several lines, remember to begin and end the string with ". This command writes directly either to the /etc/gconf/gconf.xml.mandatory/%gconf-tree.xml if it exists or to the file /etc/gconf/gconf.xml.mandatory/apps/gdm/simple-greeter/%gconf.xml. Either of these files can later be edited directly if necessary.
An appropriate warning message reinforces policy awareness during the login process and facilitates possible legal action against attackers. AC-8(a)
AC-8(c)
CCE-27379-7 All GIDs referenced in /etc/passwd must be defined in /etc/group Add a group to the system for each GID referenced without a corresponding group. If a user is assigned the Group Identifier (GID) of a group not existing on the system, and a group with the Gruop Identifier (GID) is subsequently created, the user may have unintended rights to any files associated with the group. IA-2
CM-6(a)
CCE-26785-6 Enable Auditing for Processes Which Start Prior to the Audit Daemon To ensure all processes can be audited, even those which start prior to the audit daemon, add the argument audit=1 to the kernel line in /etc/grub.conf, in the manner below:
kernel /vmlinuz-version ro vga=ext root=/dev/VolGroup00/LogVol00 rhgb quiet audit=1
Each process on the system carries an "auditable" flag which indicates whether its activities can be audited. Although auditd takes care of enabling this for all processes which launch after it does, adding the kernel argument ensures it is set for every process during boot. AC-17(1)
AU-14(1)
AU-10
CM-6(a)
IR-5(1)
CCE-27043-9 Disable Interactive Boot To disable the ability for users to perform interactive startups, perform both of the following:
  1. Edit the file /etc/sysconfig/init. Add or correct the line:
    PROMPT=no
  2. Inspect the kernel boot arguments (which follow the word kernel) in /etc/grub.conf and ensure the confirm argument is not present.
Both the PROMPT option of the /etc/sysconfig/init file and the confirm kernel boot argument of the /etc/grub.conf file allow the console user to perform an interactive system startup, in which it is possible to select the set of services which are started on boot.
Using interactive boot, the console user could disable auditing, firewalls, or other services, weakening system security. SC-2(1)
CM-6(a)
CCE-26956-3 Ensure SELinux Not Disabled in /etc/grub.conf SELinux can be disabled at boot time by an argument in /etc/grub.conf. Remove any instances of selinux=0 from the kernel arguments in that file to prevent SELinux from being disabled at boot. Disabling a major host protection feature, such as SELinux, at boot time prevents it from confining system services at boot time. Further, it increases the chances that it will remain off during system operation. AC-3
AC-3(3)(a)
CCE-26911-8 Set Boot Loader Password in grub.conf The grub boot loader should have password protection enabled to protect boot-time settings. To do so, select a password and then generate a hash from it by running the following command:
$ grub-crypt --sha-512
When prompted to enter a password, insert the following line into /etc/grub.conf immediately after the header comments. (Use the output from grub-crypt as the value of password-hash):
password --encrypted password-hash
NOTE: To meet FISMA Moderate, the bootloader password MUST differ from the root password.
Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode. CM-6(a)
CCE-26340-0 Disable Mounting of cramfs To configure the system to prevent the cramfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install cramfs /bin/true
This effectively prevents usage of this uncommon filesystem. The cramfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A cramfs image can be used without having to first decompress the image.
Removing support for unneeded filesystem types reduces the local attack surface of the server. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26448-1 Disable DCCP Support The Datagram Congestion Control Protocol (DCCP) is a relatively new transport layer protocol, designed to support streaming media and telephony. To configure the system to prevent the dccp kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install dccp /bin/true
Disabling DCCP protects the system against exploitation of any flaws in its implementation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26544-7 Disable Mounting of freevxfs To configure the system to prevent the freevxfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install freevxfs /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26800-3 Disable Mounting of hfs To configure the system to prevent the hfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install hfs /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26361-6 Disable Mounting of hfsplus To configure the system to prevent the hfsplus kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install hfsplus /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26670-0 Disable Mounting of jffs2 To configure the system to prevent the jffs2 kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install jffs2 /bin/true
This effectively prevents usage of this uncommon filesystem.
Linux kernel modules which implement filesystems that are not needed by the local system should be disabled. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26239-4 Disable RDS Support The Reliable Datagram Sockets (RDS) protocol is a transport layer protocol designed to provide reliable high-bandwidth, low-latency communications between nodes in a cluster. To configure the system to prevent the rds kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install rds /bin/true
Disabling RDS protects the system against exploitation of any flaws in its implementation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26410-1 Disable SCTP Support The Stream Control Transmission Protocol (SCTP) is a transport layer protocol, designed to support the idea of message-oriented communication, with several streams of messages within one connection. To configure the system to prevent the sctp kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install sctp /bin/true
Disabling SCTP protects the system against exploitation of any flaws in its implementation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26404-4 Disable Mounting of squashfs To configure the system to prevent the squashfs kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install squashfs /bin/true
This effectively prevents usage of this uncommon filesystem. The squashfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems (similar to cramfs). A squashfs image can be used without having to first decompress the image.
Removing support for unneeded filesystem types reduces the local attack surface of the system. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26696-5 Disable TIPC Support The Transparent Inter-Process Communication (TIPC) protocol is designed to provide communications between nodes in a cluster. To configure the system to prevent the tipc kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install tipc /bin/true
Disabling TIPC protects the system against exploitation of any flaws in its implementation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26677-5 Disable Mounting of udf To configure the system to prevent the udf kernel module from being loaded, add the following line to a file in the directory /etc/modprobe.d:
install udf /bin/true
This effectively prevents usage of this uncommon filesystem. The udf filesystem type is the universal disk format used to implement the ISO/IEC 13346 and ECMA-167 specifications. This is an open vendor filesystem type for data storage on a broad range of media. This filesystem type is neccessary to support writing DVDs and newer optical disc formats.
Removing support for unneeded filesystem types reduces the local attack surface of the system. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26778-1 Add nodev Option to /dev/shm The nodev mount option can be used to prevent creation of device files in /dev/shm. Legitimate character and block devices should not exist within temporary directories like /dev/shm. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-26622-1 Add noexec Option to /dev/shm The noexec mount option can be used to prevent binaries from being executed out of /dev/shm. It can be dangerous to allow the execution of binaries from world-writable temporary storage directories such as /dev/shm. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm. Allowing users to execute binaries from world-writable directories such as /dev/shm can expose the system to potential compromise. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-26486-1 Add nosuid Option to /dev/shm The nosuid mount option can be used to prevent execution of setuid programs in /dev/shm. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /dev/shm. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-27045-4 Add nodev Option to Non-Root Local Partitions The nodev mount option prevents files from being interpreted as character or block devices. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of any non-root local partitions. The nodev mount option prevents files from being interpreted as character or block devices. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails, for which it is not advised to set nodev on these filesystems. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-26860-7 Add nodev Option to Removable Media Partitions The nodev mount option prevents files from being interpreted as character or block devices. Legitimate character and block devices should exist only in the /dev directory on the root partition or within chroot jails built for system services. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions. The only legitimate location for device files is the /dev directory located on the root partition. An exception to this is chroot jails, and it is not advised to set nodev on partitions which contain their root filesystems. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-27196-5 Add noexec Option to Removable Media Partitions The noexec mount option prevents the direct execution of binaries on the mounted filesystem. Preventing the direct execution of binaries from removable media (such as a USB key) provides a defense against malicious software that may be present on such untrusted media. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions. Allowing users to execute binaries from removable media such as USB keys exposes the system to potential compromise. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-27056-1 Add nosuid Option to Removable Media Partitions The nosuid mount option prevents set-user-identifier (SUID) and set-group-identifier (SGID) permissions from taking effect. These permissions allow users to execute binaries with the same permissions as the owner and group of the file respectively. Users should not be allowed to introduce SUID and SGID files into the system via partitions mounted from removeable media. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions. The presence of SUID and SGID executables should be tightly controlled. Allowing users to introduce SUID or SGID binaries from partitions mounted off of removable media would allow them to introduce their own highly-privileged programs. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-26499-4 Add nodev Option to /tmp The nodev mount option can be used to prevent device files from being created in /tmp. Legitimate character and block devices should not exist within temporary directories like /tmp. Add the nodev option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. The only legitimate location for device files is the /dev directory located on the root partition. The only exception to this is chroot jails. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-26720-3 Add noexec Option to /tmp The noexec mount option can be used to prevent binaries from being executed out of /tmp. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. Allowing users to execute binaries from world-writable directories such as /tmp should never be necessary in normal operation and can expose the system to potential compromise. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-26762-5 Add nosuid Option to /tmp The nosuid mount option can be used to prevent execution of setuid programs in /tmp. The SUID and SGID permissions should not be required in these world-writable directories. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of /tmp. The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-26582-7 Bind Mount /var/tmp To /tmp The /var/tmp directory is a world-writable directory. Bind-mount it to /tmp in order to consolidate temporary storage into one location protected by the same techniques as /tmp. To do so, edit /etc/fstab and add the following line:
/tmp     /var/tmp     none     rw,nodev,noexec,nosuid,bind     0 0
See the mount(8) man page for further explanation of bind mounting.
Having multiple locations for temporary storage is not required. Unless absolutely necessary to meet requirements, the storage location /var/tmp should be bind mounted to /tmp and thus share the same protections. CM-7(a)
CM-7(b)
CM-6(a)
AC-6
AC-6(1)
MP-7
CCE-27161-9 Disable Interface Usage of IPv6 To disable interface usage of IPv6, add or correct the following lines in /etc/sysconfig/network:
NETWORKING_IPV6=no
IPV6INIT=no
CCE-26891-2 Direct root Logins Not Allowed To further limit access to the root account, administrators can disable root logins at the console by editing the /etc/securetty file. This file lists all devices the root user is allowed to login to. If the file does not exist at all, the root user can login through any communication device on the system, whether via the console or via a raw network interface. This is dangerous as user can login to the system as root via Telnet, which sends the password in plain text over the network. By default, Red Hat Enterprise Linux 6's /etc/securetty file only allows the root user to login at the console physically attached to the system. To prevent root from logging in, remove the contents of this file. To prevent direct root logins, remove the contents of this file by typing the following command:
$ sudo echo > /etc/securetty
Disabling direct root logins ensures proper accountability and multifactor authentication to privileged accounts. Users will first login, then escalate to privileged (root) access via su / sudo. This is required for FISMA Low and FISMA Moderate systems. IA-2
CM-6(a)
CCE-27038-9 Prevent Login to Accounts With Empty Password If an account is configured for password authentication but does not have an assigned password, it may be possible to log into the account without authentication. Remove any instances of the nullok option in /etc/pam.d/system-auth to prevent logins with empty passwords. If an account has an empty password, anyone could log in and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments. IA-5(1)(a)
IA-5(c)
CM-6(a)
CCE-27032-2 Ensure All Files Are Owned by a User If any files are not owned by a user, then the cause of their lack of ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate user. Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed. CM-6(a)
AC-6(1)
CCE-27225-2 Verify No netrc Files Exist The .netrc files contain login information used to auto-login into FTP servers and reside in the user's home directory. These files may contain unencrypted passwords to remote FTP servers making them susceptible to access by unauthorized users and should not be used. Any .netrc files should be removed. Unencrypted passwords for remote FTP servers may be stored in .netrc files. IA-5(h)
IA-5(1)(c)
CM-6(a)
IA-5(7)
CCE-27270-8 Remove Rsh Trust Files The files /etc/hosts.equiv and ~/.rhosts (in each user's home directory) list remote hosts and users that are trusted by the local system when using the rshd daemon. To remove these files, run the following command to delete them from any location:
$ sudo rm /etc/hosts.equiv
$ rm ~/.rhosts
This action is only meaningful if .rhosts support is permitted through PAM. Trust files are convenient, but when used in conjunction with the R-services, they can allow unauthenticated access to a system. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26966-2 Ensure that System Accounts Do Not Run a Shell Upon Login Some accounts are not associated with a human user of the system, and exist to perform some administrative function. Should an attacker be able to log into these accounts, they should not be granted access to a shell.

The login shell for each local account is stored in the last field of each line in /etc/passwd. System accounts are those user accounts with a user ID less than UID_MIN, where value of UID_MIN directive is set in /etc/login.defs configuration file. In the default configuration UID_MIN is set to 1000, thus system accounts are those user accounts with a user ID less than 1000. The user ID is stored in the third field. If any system account SYSACCT (other than root) has a login shell, disable it with the command:
$ sudo usermod -s /sbin/nologin SYSACCT
Ensuring shells are not given to system accounts upon login makes it more difficult for attackers to make use of system accounts. AC-6
CM-6(a)
CCE-26958-9 Specify Additional Remote NTP Servers Additional NTP servers can be specified for time synchronization in the file /etc/ntp.conf. To do so, add additional lines of the following form, substituting the IP address or hostname of a remote NTP server for ntpserver:
server ntpserver
Specifying additional NTP servers increases the availability of accurate time data, in the event that one of the specified servers becomes unavailable. This is typical for a system acting as an NTP server for other systems. CM-6(a)
AU-8(1)(a)
AU-8(2)
CCE-27098-3 Specify a Remote NTP Server To specify a remote NTP server for time synchronization, edit the file /etc/ntp.conf. Add or correct the following lines, substituting the IP or hostname of a remote NTP server for ntpserver:
server ntpserver
This instructs the NTP software to contact that remote server to obtain time data.
Synchronizing with an NTP server makes it possible to collate system logs from multiple sources or correlate computer events with real time events. CM-6(a)
AU-8(1)(a)
CCE-27024-9 Install AIDE The aide package can be installed with the following command:
$ sudo yum install aide
The AIDE package must be installed if it is to be available for integrity checking. CM-6(a)
CCE-27030-6 Uninstall bind Package The named service is provided by the bind package. The bind package can be removed with the following command:
$ sudo yum erase bind
If there is no need to make DNS server software available, removing it provides a safeguard against its activation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27120-5 Uninstall DHCP Server Package If the system does not need to act as a DHCP server, the dhcp package can be uninstalled. The dhcp package can be removed with the following command:
$ sudo yum erase dhcp
Removing the DHCP server ensures that it cannot be easily or accidentally reactivated and disrupt network operation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27039-7 Uninstall dovecot Package The dovecot package can be removed with the following command:
$ sudo yum erase dovecot
If there is no need to make the Dovecot software available, removing it provides a safeguard against its activation.
CCE-27133-8 Uninstall httpd Package The httpd package can be removed with the following command:
 $ sudo yum erase httpd
If there is no need to make the web server software available, removing it provides a safeguard against its activation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27404-3 Uninstall mcstrans Package The mcstransd daemon provides category label information to client processes requesting information. The label translations are defined in /etc/selinux/targeted/setrans.conf. The mcstrans package can be removed with the following command:
$ sudo yum erase mcstrans
Since this service is not used very often, disable it to reduce the amount of potentially vulnerable code running on the system. NOTE: This rule was added in support of the CIS RHEL6 v1.2.0 benchmark. Please note that Red Hat does not feel this rule is security relevant.
CCE-26332-7 Uninstall net-snmp Package The net-snmp package provides the snmpd service. The net-snmp package can be removed with the following command:
$ sudo yum erase net-snmp
If there is no need to run SNMP server software, removing the package provides a safeguard against its activation.
CCE-26858-1 Uninstall openldap-servers Package The openldap-servers RPM is not installed by default on a Red Hat Enterprise Linux 6 system. It is needed only by the OpenLDAP server, not by the clients which use LDAP for authentication. If the system is not intended for use as an LDAP Server it should be removed. Unnecessary packages should not be installed to decrease the attack surface of the system. While this software is clearly essential on an LDAP server, it is not necessary on typical desktop or workstation systems. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27062-9 Uninstall rsh-server Package The rsh-server package can be removed with the following command:
$ sudo yum erase rsh-server
The rsh-server service provides unencrypted remote access service which does not provide for the confidentiality and integrity of user passwords or the remote session and has very weak authentication. If a privileged user were to login using this service, the privileged user password could be compromised. The rsh-server package provides several obsolete and insecure network services. Removing it decreases the risk of those services' accidental (or intentional) activation. CM-7(a)
CM-7(b)
CM-6(a)
IA-5(1)(c)
CCE-27359-9 Uninstall rsh Package The rsh package contains the client commands for the rsh services These legacy clients contain numerous security exposures and have been replaced with the more secure SSH package. Even if the server is removed, it is best to ensure the clients are also removed to prevent users from inadvertently attempting to use these commands and therefore exposing their credentials. Note that removing the rsh package removes the clients for rsh,rcp, and rlogin.
CCE-26809-4 Ensure rsyslog is Installed Rsyslog is installed by default. The rsyslog package can be installed with the following command:
 $ sudo yum install rsyslog
The rsyslog package provides the rsyslog daemon, which provides system logging services. CM-6(a)
CCE-27102-3 Uninstall Samba Package The samba package can be removed with the following command:
 $ sudo yum erase samba
If there is no need to make the Samba software available, removing it provides a safeguard against its activation.
CCE-27421-7 Uninstall setroubleshoot Package The SETroubleshoot service notifies desktop users of SELinux denials. The service provides information around configuration errors, unauthorized intrusions, and other potential errors. The setroubleshoot package can be removed with the following command:
$ sudo yum erase setroubleshoot
The SETroubleshoot service is an unnecessary daemon to have running on a server, especially if X Windows is removed or disabled.
CCE-26977-9 Uninstall squid Package The squid package can be removed with the following command:
 $ sudo yum erase squid
If there is no need to make the proxy server software available, removing it provides a safeguard against its activation.
CCE-27427-4 Uninstall talk-server Package The talk-server package can be removed with the following command:
 $ sudo yum erase talk-server
The talk software presents a security risk as it uses unencrypted protocols for communications. Removing the talk-server package decreases the risk of the accidental (or intentional) activation of talk services.
CCE-27373-0 Uninstall talk Package The talk package contains the client program for the Internet talk protocol, which allows the user to chat with other users on different systems. Talk is a communication program which copies lines from one terminal to the terminal of another user. The talk package can be removed with the following command:
$ sudo yum erase talk
The talk software presents a security risk as it uses unencrypted protocols for communications. Removing the talk package decreases the risk of the accidental (or intentional) activation of talk client program.
CCE-27073-6 Uninstall telnet-server Package The telnet-server package can be removed with the following command:
$ sudo yum erase telnet-server
It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities are often overlooked and therefore may remain unsecure. They increase the risk to the platform by providing additional attack vectors.
The telnet service provides an unencrypted remote access service which does not provide for the confidentiality and integrity of user passwords or the remote session. If a privileged user were to login using this service, the privileged user password could be compromised.
Removing the telnet-server package decreases the risk of the telnet service's accidental (or intentional) activation.
CM-7(a)
CM-7(b)
CM-6(a)
CCE-27428-2 Remove telnet Clients The telnet client allows users to start connections to other systems via the telnet protocol. The telnet protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal credentials. The ssh package provides an encrypted session and stronger security and is included in Red Hat Enterprise Linux 6.
CCE-26946-4 Uninstall tftp-server Package The tftp-server package can be removed with the following command:
 $ sudo yum erase tftp-server
Removing the tftp-server package decreases the risk of the accidental (or intentional) activation of tftp services.

If TFTP is required for operational support (such as transmission of router configurations), its use must be documented with the Information Systems Securty Manager (ISSM), restricted to only authorized personnel, and have access control rules established.
CM-7(a)
CM-7(b)
CM-6(a)
CCE-27448-0 Remove tftp Daemon Trivial File Transfer Protocol (TFTP) is a simple file transfer protocol, typically used to automatically transfer configuration or boot files between systems. TFTP does not support authentication and can be easily hacked. The package tftp is a client program that allows for connections to a tftp server. It is recommended that TFTP be removed, unless there is a specific need for TFTP (such as a boot server). In that case, use extreme caution when configuring the services.
CCE-26687-4 Uninstall vsftpd Package The vsftpd package can be removed with the following command:
 $ sudo yum erase vsftpd
Removing the vsftpd package decreases the risk of its accidental activation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27005-8 Uninstall xinetd Package The xinetd package can be removed with the following command:
$ sudo yum erase xinetd
Removing the xinetd package decreases the risk of the xinetd service's accidental (or intentional) activation. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27198-1 Remove the X Windows Package Group By removing the xorg-x11-server-common package, the system no longer has X Windows installed. If X Windows is not installed then the system cannot boot into graphical user mode. This prevents the system from being accidentally or maliciously booted into a graphical.target mode. To do so, run the following command:
$ sudo yum groupremove "X Window System"
$ sudo yum remove xorg-x11-server-common
Unnecessary service packages must not be installed to decrease the attack surface of the system. X windows has a long history of security vulnerabilities and should not be installed unless approved and documented. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27372-2 Remove NIS Client The Network Information Service (NIS), formerly known as Yellow Pages, is a client-server directory service protocol used to distribute system configuration files. The NIS client (ypbind) was used to bind a system to an NIS server and receive the distributed configuration files. The NIS service is inherently an insecure system that has been vulnerable to DOS attacks, buffer overflows and has poor authentication for querying NIS maps. NIS generally has been replaced by such protocols as Lightweight Directory Access Protocol (LDAP). It is recommended that the service be removed.
CCE-27079-3 Uninstall ypserv Package The ypserv package can be removed with the following command:
$ sudo yum erase ypserv
The NIS service provides an unencrypted authentication service which does not provide for the confidentiality and integrity of user passwords or the remote session. Removing the ypserv package decreases the risk of the accidental (or intentional) activation of NIS or NIS+ services. CM-7(a)
CM-7(b)
CM-6(a)
IA-5(1)(c)
CCE-26557-9 Ensure /home Located On Separate Partition If user home directories will be stored locally, create a separate partition for /home at installation time (or migrate it later using LVM). If /home will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later. Ensuring that /home is mounted on its own partition enables the setting of more restrictive mount options, and also helps ensure that users cannot trivially fill partitions used for log or audit data storage. SC-32
CCE-26435-8 Ensure /tmp Located On Separate Partition The /tmp directory is a world-writable directory used for temporary file storage. Ensure it has its own partition or logical volume at installation time, or migrate it using LVM. The /tmp partition is used as temporary storage by many programs. Placing /tmp in its own partition enables the setting of more restrictive mount options, which can help protect programs which use it. SC-32
CCE-81045-7 Ensure /var Located On Separate Partition The /var directory is used by daemons and other system services to store frequently-changing data. Ensure that /var has its own partition or logical volume at installation time, or migrate it using LVM. Ensuring that /var is mounted on its own partition enables the setting of more restrictive mount options. This helps protect system services such as daemons or other programs which use it. It is not uncommon for the /var directory to contain world-writable directories installed by other software packages. SC-32
CCE-26215-4 Ensure /var/log Located On Separate Partition System logs are stored in the /var/log directory. Ensure that it has its own partition or logical volume at installation time, or migrate it using LVM. Placing /var/log in its own partition enables better separation between log files and other files in /var/. CM-6(a)
AU-4
SC-5(2)
CCE-26436-6 Ensure /var/log/audit Located On Separate Partition Audit logs are stored in the /var/log/audit directory. Ensure that it has its own partition or logical volume at installation time, or migrate it later using LVM. Make absolutely certain that it is large enough to store all audit logs that will be created by the auditing daemon. Placing /var/log/audit in its own partition enables better separation between audit files and other files, and helps ensure that auditing cannot be halted due to the partition running out of space. SC-32
CCE-26780-7 Disable Postfix Network Listening Edit the file /etc/postfix/main.cf to ensure that only the following inet_interfaces line appears:
inet_interfaces = 
This ensures postfix accepts mail messages (such as cron job reports) from the local system only, and not from the network, which protects it from network attack. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27040-5 Require Authentication for Single User Mode Single-user mode is intended as a system recovery method, providing a single user root access to the system by providing a boot option at startup. By default, no authentication is performed if single-user mode is selected.

To require entry of the root password even if the system is started in single-user mode, add or correct the following line in the file /etc/sysconfig/init:
SINGLE=/sbin/sulogin
This prevents attackers with physical access from trivially bypassing security on the machine and gaining root access. Such accesses are further prevented by configuring the bootloader password. IA-2
AC-3
CM-6(a)
CCE-27125-4 Root Path Must Be Vendor Default Assuming root shell is bash, edit the following files:
~/.profile
~/.bashrc
Change any PATH variables to the vendor default for root and remove any empty PATH entries or references to relative paths.
The root account's executable search path must be the vendor default, and must contain only absolute paths. CM-6(a)
CCE-27223-7 Verify File Hashes with RPM Without cryptographic integrity protections, system executables and files can be altered by unauthorized users without detection. The RPM package management system can check the hashes of installed software packages, including many that are important to system security. To verify that the cryptographic hash of system files and commands match vendor values, run the following command to list which files on the system have hashes that differ from what is expected by the RPM database:
$ rpm -Va | grep '^..5'
A "c" in the second column indicates that a file is a configuration file, which may appropriately be expected to change. If the file was not expected to change, investigate the cause of the change using audit logs or other means. The package can then be reinstalled to restore the file. Run the following command to determine which package owns the file:
$ rpm -qf FILENAME
The package can be reinstalled from a yum repository using the command:
$ sudo yum reinstall PACKAGENAME
Alternatively, the package can be reinstalled from trusted media using the command:
$ sudo rpm -Uvh PACKAGENAME
The hashes of important files like system executables should match the information given by the RPM database. Executables with erroneous hashes could be a sign of nefarious activity on the system. CM-6(d)
CM-6(c)
SI-7
SI-7(1)
SI-7(6)
AU-9(3)
CCE-26731-0 Verify and Correct File Permissions with RPM The RPM package management system can check file access permissions of installed software packages, including many that are important to system security. Verify that the file permissions of system files and commands match vendor values. Check the file permissions with the following command:
$ sudo rpm -Va | awk '{ if (substr($0,2,1)=="M") print $NF }'
Output indicates files that do not match vendor defaults. After locating a file with incorrect permissions, run the following command to determine which package owns it:
$ rpm -qf FILENAME

Next, run the following command to reset its permissions to the correct values:
$ sudo rpm --setperms PACKAGENAME
Permissions on system binaries and configuration files that are too generous could allow an unauthorized user to gain privileges that they should not have. The permissions set by the vendor should be maintained. Any deviations from this baseline should be investigated. SI-7
CCE-27190-8 Ensure System Log Files Have Correct Permissions The file permissions for all log files written by rsyslog should be set to 600, or more restrictive. These log files are determined by the second part of each Rule line in /etc/rsyslog.conf and typically all appear in /var/log. For each log file LOGFILE referenced in /etc/rsyslog.conf, run the following command to inspect the file's permissions:
$ ls -l LOGFILE
If the permissions are not 600 or more restrictive, run the following command to correct this:
$ sudo chmod 0600 LOGFILE
"
Log files can contain valuable information regarding system configuration. If the system log files are not protected unauthorized users could change the logged data, eliminating their forensic value. CM-6(a)
AC-6(1)
CCE-26803-7 Ensure rsyslog Does Not Accept Remote Messages Unless Acting As Log Server The rsyslog daemon should not accept remote messages unless the system acts as a log server. To ensure that it is not listening on the network, ensure the following lines are not found in /etc/rsyslog.conf:
$ModLoad imtcp
$InputTCPServerRun port
$ModLoad imudp
$UDPServerRun port
$ModLoad imrelp
$InputRELPServerRun port
Any process which receives messages from the network incurs some risk of receiving malicious messages. This risk can be eliminated for rsyslog by configuring it not to listen on the network. CM-7(a)
CM-7(b)
CM-6(a)
CCE-26801-1 Ensure Logs Sent To Remote Host To configure rsyslog to send logs to a remote log server, open /etc/rsyslog.conf and read and understand the last section of the file, which describes the multiple directives necessary to activate remote logging. Along with these other directives, the system can be configured to forward its logs to a particular log server by adding or correcting one of the following lines, substituting appropriately. The choice of protocol depends on the environment of the system; although TCP and RELP provide more reliable message delivery, they may not be supported in all environments.
To use UDP for log message delivery:
*.* @

To use TCP for log message delivery:
*.* @@

To use RELP for log message delivery:
*.* :omrelp:

There must be a resolvable DNS CNAME or Alias record set to "" for logs to be sent correctly to the centralized logging utility.
A log server (loghost) receives syslog messages from one or more systems. This data can be used as an additional log source in the event a system is compromised and its local logs are suspect. Forwarding log messages to a remote loghost also provides system administrators with a centralized place to view the status of multiple hosts within the enterprise. CM-6(a)
AU-4(1)
AU-9(2)
CCE-27111-4 Ensure No Daemons are Unconfined by SELinux Daemons for which the SELinux policy does not contain rules will inherit the context of the parent process. Because daemons are launched during startup and descend from the init process, they inherit the initrc_t context.

To check for unconfined daemons, run the following command:
$ sudo ps -eZ | egrep "initrc" | egrep -vw "tr|ps|egrep|bash|awk" | tr ':' ' ' | awk '{ print $NF }'
It should produce no output in a well-configured system.
Daemons which run with the initrc_t context may cause AVC denials, or allow privileges that the daemon does not require. CM-7(a)
CM-7(b)
CM-6(a)
AC-3(3)(a)
AC-6
CCE-26875-5 Configure SELinux Policy The SELinux targeted policy is appropriate for general-purpose desktops and servers, as well as systems in many other roles. To configure the system to use this policy, add or correct the following line in /etc/selinux/config:
SELINUXTYPE=
Other policies, such as mls, provide additional security labeling and greater confinement but are not compatible with many general-purpose use cases.
Setting the SELinux policy to targeted or a more specialized policy ensures the system will confine processes that are likely to be targeted for exploitation, such as network or system services.

Note: During the development or debugging of SELinux modules, it is common to temporarily place non-production systems in permissive mode. In such temporary cases, SELinux policies should be developed, and once work is completed, the system should be reconfigured to .
AC-3
AC-3(3)(a)
AU-9
SC-7(21)
CCE-26969-6 Ensure SELinux State is Enforcing The SELinux state should be set to at system boot time. In the file /etc/selinux/config, add or correct the following line to configure the system to boot into enforcing mode:
SELINUX=
Setting the SELinux state to enforcing ensures SELinux is able to confine potentially compromised processes to the security policy, which is designed to prevent them from causing damage to the system or further elevating their privileges. AC-3
AC-3(3)(a)
AU-9
SC-7(21)
CCE-27249-2 Disable At Service (atd) The at and batch commands can be used to schedule tasks that are meant to be executed only once. This allows delayed execution in a manner similar to cron, except that it is not recurring. The daemon atd keeps track of tasks scheduled via at and batch, and executes them at the specified time. The atd service can be disabled with the following command:
$ sudo chkconfig atd off
The atd service could be used by an unsophisticated insider to carry out activities outside of a normal login session, which could complicate accountability. Furthermore, the need to schedule tasks with at or batch is not common. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27058-7 Enable auditd Service The auditd service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The auditd service can be enabled with the following command:
$ sudo chkconfig --level 2345 auditd on
Without establishing what type of events occurred, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack. Ensuring the auditd service is active ensures audit records generated by the kernel are appropriately recorded.

Additionally, a properly configured audit subsystem ensures that actions of individual system users can be uniquely traced to those users so they can be held accountable for their actions.
AC-2(g)
AU-3
AU-10
AU-2(d)
AU-12(c)
AU-14(1)
AC-6(9)
CM-6(a)
CCE-27087-6 Disable Avahi Server Software The avahi-daemon service can be disabled with the following command:
$ sudo chkconfig avahi-daemon off
Because the Avahi daemon service keeps an open network port, it is subject to network attacks. Its functionality is convenient but is only appropriate if the local network can be trusted. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27070-2 Enable cron Service The crond service is used to execute commands at preconfigured times. It is required by almost all systems to perform necessary maintenance tasks, such as notifying root of system activity. The crond service can be enabled with the following command:
$ sudo chkconfig --level 2345 crond on
Due to its usage for maintenance and security-supporting tasks, enabling the cron daemon is essential. CM-6(a)
CCE-26899-5 Disable the CUPS Service The cups service can be disabled with the following command:
$ sudo chkconfig cups off
Turn off unneeded services to reduce attack surface. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27006-6 Verify ip6tables Enabled if Using IPv6 The ip6tables service can be enabled with the following command:
$ sudo chkconfig --level 2345 ip6tables on
The ip6tables service provides the system's host-based firewalling capability for IPv6 and ICMPv6. AC-4
CM-7(b)
CA-3(5)
SC-7(21)
CM-6(a)
CCE-27018-1 Verify iptables Enabled The iptables service can be enabled with the following command:
$ sudo chkconfig --level 2345 iptables on
The iptables service provides the system's host-based firewalling capability for IPv4 and ICMP. AC-4
CM-7(b)
CA-3(5)
SC-7(21)
CM-6(a)
CCE-27104-9 Disable Network File System Lock Service (nfslock) The Network File System Lock (nfslock) service starts the required remote procedure call (RPC) processes which allow clients to lock files on the server. If the local system is not configured to mount NFS filesystems then this service should be disabled. The nfslock service can be disabled with the following command:
$ sudo chkconfig nfslock off
CCE-27093-4 Enable the NTP Daemon The ntpd service can be enabled with the following command:
$ sudo chkconfig --level 2345 ntpd on
Enabling the ntpd service ensures that the ntpd service will be running and that the system will synchronize its time to any servers specified. This is important whether the system is configured to be a client (and synchronize only its own clock) or it is also acting as an NTP server to other systems. Synchronizing time is essential for authentication services such as Kerberos, but it is also important for maintaining accurate logs and auditing possible security breaches.

The NTP daemon offers all of the functionality of ntpdate, which is now deprecated. Additional information on this is available at http://support.ntp.org/bin/view/Dev/DeprecatingNtpdate.
CM-6(a)
AU-8(1)(a)
CCE-26846-6 Disable Red Hat Network Service (rhnsd) The Red Hat Network service automatically queries Red Hat Network servers to determine whether there are any actions that should be executed, such as package updates. This only occurs if the system was registered to an RHN server or satellite and managed as such. The rhnsd service can be disabled with the following command:
$ sudo chkconfig rhnsd off
Although systems management and patching is extremely important to system security, management by a system outside the enterprise enclave is not desirable for some environments. However, if the system is being managed by RHN or RHN Satellite Server the rhnsd daemon can remain on. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27430-8 Disable rpcbind Service The rpcbind utility maps RPC services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they are listening on and the RPC program numbers they expect to serve. The rpcbind service redirects the client to the proper port number so it can communicate with the requested service. If the system does not require RPC (such as for NFS servers) then this service should be disabled. The rpcbind service can be disabled with the following command:
$ sudo chkconfig rpcbind off
If the system does not require rpc based services, it is recommended that rpcbind be disabled to reduce the attack surface.
CCE-26864-9 Disable Secure RPC Client Service (rpcgssd) The rpcgssd service manages RPCSEC GSS contexts required to secure protocols that use RPC (most often Kerberos and NFS). The rpcgssd service is the client-side of RPCSEC GSS. If the system does not require secure RPC then this service should be disabled. The rpcgssd service can be disabled with the following command:
$ sudo chkconfig rpcgssd off
CCE-26870-6 Disable RPC ID Mapping Service (rpcidmapd) The rpcidmapd service is used to map user names and groups to UID and GID numbers on NFSv4 mounts. If NFS is not in use on the local system then this service should be disabled. The rpcidmapd service can be disabled with the following command:
$ sudo chkconfig rpcidmapd off
CCE-27122-1 Disable Secure RPC Server Service (rpcsvcgssd) The rpcsvcgssd service manages RPCSEC GSS contexts required to secure protocols that use RPC (most often Kerberos and NFS). The rpcsvcgssd service is the server-side of RPCSEC GSS. If the system does not require secure RPC then this service should be disabled. The rpcsvcgssd service can be disabled with the following command:
$ sudo chkconfig rpcsvcgssd off
Unnecessary services should be disabled to decrease the attack surface of the system.
CCE-26807-8 Enable rsyslog Service The rsyslog service provides syslog-style logging by default on Red Hat Enterprise Linux 6. The rsyslog service can be enabled with the following command:
$ sudo chkconfig --level 2345 rsyslog on
The rsyslog service must be running in order to provide logging services, which are essential to system administration. CM-6(a)
AU-4(1)
CCE-27072-8 Allow Only SSH Protocol 2 Only SSH protocol version 2 connections should be permitted. The default setting in /etc/ssh/sshd_config is correct, and can be verified by ensuring that the following line appears:
Protocol 2
SSH protocol version 1 is an insecure implementation of the SSH protocol and has many well-known vulnerability exploits. Exploits of the SSH daemon could provide immediate root access to the system. CM-6(a)
AC-17(a)
AC-17(2)
IA-5(1)(c)
SC-13
MA-4(6)
CCE-26887-0 Disable SSH Access via Empty Passwords To explicitly disallow SSH login from accounts with empty passwords, add or correct the following line in /etc/ssh/sshd_config:
PermitEmptyPasswords no

Any accounts with empty passwords should be disabled immediately, and PAM configuration should prevent users from being able to assign themselves empty passwords.
Configuring this setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere. AC-17(a)
CM-7(a)
CM-7(b)
CM-6(a)
CCE-27100-7 Disable SSH Root Login The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in /etc/ssh/sshd_config:
PermitRootLogin no
Even though the communications channel may be encrypted, an additional layer of security is gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account provides individual accountability of actions performed on the system and also helps to minimize direct attack attempts on root's password. AC-6(2)
AC-17(a)
IA-2
IA-2(5)
CM-7(a)
CM-7(b)
CM-6(a)
CCE-27112-2 Enable SSH Warning Banner To enable the warning banner and ensure it is consistent across the system, add or correct the following line in /etc/ssh/sshd_config:
Banner /etc/issue
Another section contains information on how to create an appropriate system-wide warning banner.
The warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers. Alternatively, systems whose ownership should not be obvious should ensure usage of a banner that does not provide easy attribution. AC-8(a)
AC-8(c)
AC-17(a)
CM-6(a)
CCE-27556-0 Limit Users' SSH Access By default, the SSH configuration allows any user with an account to access the system. In order to specify the users that are allowed to login via SSH and deny all other users, add or correct the following line in the /etc/ssh/sshd_config file:
DenyUsers USER1 USER2
Where USER1 and USER2 are valid user names.
Specifying which accounts are allowed SSH access into the system reduces the possibility of unauthorized access to the system. AC-3
CM-6(a)
CCE-26919-1 Set SSH Idle Timeout Interval SSH allows administrators to set an idle timeout interval. After this interval has passed, the idle user will be automatically logged out.

To set an idle timeout interval, edit the following line in /etc/ssh/sshd_config as follows:
ClientAliveInterval 


The timeout interval is given in seconds. For example, have a timeout of 10 minutes, set interval to 600.

If a shorter timeout has already been set for the login shell, that value will preempt any SSH setting made in /etc/ssh/sshd_config. Keep in mind that some processes may stop SSH from correctly detecting that the user is idle.
Terminating an idle ssh session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been let unattended. CM-6(a)
AC-17(a)
AC-2(5)
AC-12
AC-17(a)
SC-10
CM-6(a)
CCE-26555-3 Use Only FIPS 140-2 Validated Ciphers Limit the ciphers to those algorithms which are FIPS-approved. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in /etc/ssh/sshd_config demonstrates use of FIPS-approved ciphers:
Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc
The man page sshd_config(5) contains a list of supported ciphers. The rule is parametrized to use the following ciphers: .
Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and system data may be compromised.
Operating systems utilizing encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.
FIPS 140-2 is the current standard for validating that mechanisms used to access cryptographic modules utilize authentication that meets industry and government requirements. For government systems, this allows Security Levels 1, 2, 3, or 4 for use on Red Hat Enterprise Linux 6.
CM-6(a)
AC-17(a)
AC-17(2)
SC-13
MA-4(6)
IA-5(1)(c)
SC-12(2)
SC-12(3)
CCE-27044-7 Disable Core Dumps for SUID programs To set the runtime status of the fs.suid_dumpable kernel parameter, run the following command:
$ sudo sysctl -w fs.suid_dumpable=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
fs.suid_dumpable = 0
The core dump of a setuid program is more likely to contain sensitive data, as the program itself runs with greater privileges than the user who initiated execution of the program. Disabling the ability for any setuid program to write a core file decreases the risk of unauthorized access of such data. SI-11(a)
SI-11(b)
Enable ExecShield via sysctl By default on Red Hat Enterprise Linux 7 64-bit systems, ExecShield is enabled and can only be disabled if the hardware does not support ExecShield or is disabled in /etc/default/grub. For Red Hat Enterprise Linux 7 32-bit systems, sysctl can be used to enable ExecShield. ExecShield uses the segmentation feature on all x86 systems to prevent execution in memory higher than a certain address. It writes an address as a limit in the code segment descriptor, to control where code can be executed, on a per-process basis. When the kernel places a process's memory regions such as the stack and heap higher than this address, the hardware prevents execution in that address range. This is enabled by default on the latest Red Hat and Fedora systems if supported by the hardware. SC-39
CM-6(a)
CCE-26999-3 Enable Randomized Layout of Virtual Address Space To set the runtime status of the kernel.randomize_va_space kernel parameter, run the following command:
$ sudo sysctl -w kernel.randomize_va_space=2
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
kernel.randomize_va_space = 2
Address space layout randomization (ASLR) makes it more difficult for an attacker to predict the location of attack code they have introduced into a process's address space during an attempt at exploitation. Additionally, ASLR makes it more difficult for an attacker to know the location of existing code in order to re-purpose it using return oriented programming (ROP) techniques. SC-30
SC-30(2)
CM-6(a)
CCE-27027-2 Disable Accepting ICMP Redirects for All IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.accept_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.accept_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required."
CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-27037-1 Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.accept_source_route kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.accept_source_route = 0
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.
CM-7(a)
CM-7(b)
SC-5CM-6(a)
SC-7(a)
CCE-27066-0 Enable Kernel Parameter to Log Martian Packets on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.log_martians kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.log_martians=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.log_martians = 1
The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected. AC-3(10)
CCE-26979-5 Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.rp_filter kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.rp_filter=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.rp_filter = 1
Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks. CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-26854-0 Disable Kernel Parameter for Accepting Secure ICMP Redirects on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.secure_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.secure_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.secure_redirects = 0
Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required. CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-27004-1 Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces To set the runtime status of the net.ipv4.conf.all.send_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.all.send_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.all.send_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.
CM-7(a)
CM-7(b)
SC-5CM-6(a)
SC-7(a)
CCE-27015-7 Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv4 Interfaces To set the runtime status of the net.ipv4.conf.default.accept_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.accept_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.
This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required.
CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-26983-7 Disable Kernel Parameter for Accepting Source-Routed Packets on IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.accept_source_route kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.accept_source_route = 0
Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures.
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required, such as when IPv4 forwarding is enabled and the system is legitimately functioning as a router.
CM-7(a)
CM-7(b)
SC-5
SC-7(a)
CCE-26915-9 Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.rp_filter kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.rp_filter=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.rp_filter = 1
Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks. CM-7(a)
CM-7(b)
CM-6(a)
SC-7(a)
CCE-26831-8 Configure Kernel Parameter for Accepting Secure Redirects By Default To set the runtime status of the net.ipv4.conf.default.secure_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.secure_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.secure_redirects = 0
Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required. CM-7(a)
CM-7(b)
SC-5
SC-7(a)
CCE-27001-7 Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces by Default To set the runtime status of the net.ipv4.conf.default.send_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.conf.default.send_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.conf.default.send_redirects = 0
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.
The ability to send ICMP redirects is only appropriate for systems acting as routers.
CM-7(a)
CM-7(b)
SC-5CM-6(a)
SC-7(a)
CCE-26883-9 Enable Kernel Parameter to Ignore ICMP Broadcast Echo Requests on IPv4 Interfaces To set the runtime status of the net.ipv4.icmp_echo_ignore_broadcasts kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.icmp_echo_ignore_broadcasts = 1
Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks.
Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.
CM-7(a)
CM-7(b)
SC-5
CCE-26993-6 Enable Kernel Parameter to Ignore Bogus ICMP Error Responses on IPv4 Interfaces To set the runtime status of the net.ipv4.icmp_ignore_bogus_error_responses kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.icmp_ignore_bogus_error_responses = 1
Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged. CM-7(a)
CM-7(b)
SC-5
CCE-26866-4 Disable Kernel Parameter for IP Forwarding on IPv4 Interfaces To set the runtime status of the net.ipv4.ip_forward kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.ip_forward=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.ip_forward = 0
Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network. CM-7(a)
CM-7(b)
SC-5CM-6(a)
SC-7(a)
CCE-27053-8 Enable Kernel Parameter to Use TCP Syncookies on IPv4 Interfaces To set the runtime status of the net.ipv4.tcp_syncookies kernel parameter, run the following command:
$ sudo sysctl -w net.ipv4.tcp_syncookies=1
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv4.tcp_syncookies = 1
A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected, and enables the system to continue servicing valid connection requests. CM-7(a)
CM-7(b)
SC-5(1)
SC-5(2)
SC-5(3)(a)
CM-6(a)
CCE-27164-3 Disable Accepting Router Advertisements on all IPv6 Interfaces by Default To set the runtime status of the net.ipv6.conf.default.accept_ra kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.default.accept_ra=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.default.accept_ra = 0
An illicit router advertisement message could result in a man-in-the-middle attack. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27166-8 Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv6 Interfaces To set the runtime status of the net.ipv6.conf.default.accept_redirects kernel parameter, run the following command:
$ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0
To make sure that the setting is persistent, add the following line to a file in the directory /etc/sysctl.d:
net.ipv6.conf.default.accept_redirects = 0
An illicit ICMP redirect message could result in a man-in-the-middle attack. CM-7(a)
CM-7(b)
CM-6(a)
CCE-27031-4 Set Daemon Umask The file /etc/init.d/functions includes initialization parameters for most or all daemons started at boot time. Many daemons on the system already individually restrict themselves to a umask of 077 in their own init scripts. By default, the umask of 022 is set which prevents creation of group- or world-writable files. To set the umask for daemons expected by the profile, edit the following line:
umask 
The umask influences the permissions assigned to files created by a process at run time. An unnecessarily permissive umask could result in files being created with insecure permissions. CM-6(a)
AC-6(1)
CCE-26878-9 Disable WiFi or Bluetooth in BIOS Some machines that include built-in wireless support offer the ability to disable the device through the BIOS. This is hardware-specific; consult your hardware manual or explore the BIOS setup during boot. Disabling wireless support in the BIOS prevents easy activation of the wireless interface, generally requiring administrators to reboot the system first. AC-18(a)
AC-18(3)
CM-7(a)
CM-7(b)
CM-6(a)
MP-7
CCE-27057-9 Deactivate Wireless Network Interfaces Deactivating wireless network interfaces should prevent normal usage of the wireless capability.

Configure the system to disable all wireless network interfaces with the following command:
$ sudo nmcli radio wifi off
The use of wireless networking can introduce many different attack vectors into the organization's network. Common attack vectors such as malicious association and ad hoc networks will allow an attacker to spoof a wireless access point (AP), allowing validated systems to connect to the malicious AP and enabling the attacker to monitor and record network traffic. These malicious APs can also serve to create a man-in-the-middle attack or be used to create a denial of service to valid network resources. AC-18(a)
AC-18(3)
CM-7(a)
CM-7(b)
CM-6(a)
MP-7