Rules with PCI DSS Reference in Guide to the Secure Configuration of Red Hat Enterprise Linux 6


Reference (PCI DSS) Rule Title Description Rationale Variable Setting
Req-10.4.3 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.
Req-10.4.1 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.
Req-10.4.3 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.
Req-8.1.8 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. To have a timeout of 15 minutes, set interval to 900.

If a shorter timeout has already been set for the login shell, that value will preempt any SSH setting made here. Keep in mind that some processes may stop SSH from correctly detecting that the user is idle.
Causing idle users to be automatically logged out guards against compromises one system leading trivially to compromises on another.
Req-10.5.1 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.
Req-10.5.2 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.
Req-10.5.1 Ensure Log Files Are Owned By Appropriate User The owner of all log files written by rsyslog should be root. 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 owner:
$ ls -l LOGFILE
If the owner is not root, run the following command to correct this:
$ sudo chown root LOGFILE
The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.
Req-10.5.2 Ensure Log Files Are Owned By Appropriate User The owner of all log files written by rsyslog should be root. 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 owner:
$ ls -l LOGFILE
If the owner is not root, run the following command to correct this:
$ sudo chown root LOGFILE
The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.
Req-10.5.1 Ensure Log Files Are Owned By Appropriate Group The group-owner of all log files written by rsyslog should be root. 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 group owner:
$ ls -l LOGFILE
If the owner is not root, run the following command to correct this:
$ sudo chgrp root LOGFILE
The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.
Req-10.5.2 Ensure Log Files Are Owned By Appropriate Group The group-owner of all log files written by rsyslog should be root. 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 group owner:
$ ls -l LOGFILE
If the owner is not root, run the following command to correct this:
$ sudo chgrp root LOGFILE
The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.
Req-8.2.1 Set Password Hashing Algorithm in /etc/login.defs In /etc/login.defs, add or correct the following line to ensure the system will use SHA-512 as the hashing algorithm:
ENCRYPT_METHOD SHA512
Using a stronger hashing algorithm makes password cracking attacks more difficult.
Req-8.2.1 Set Password Hashing Algorithm in /etc/libuser.conf In /etc/libuser.conf, add or correct the following line in its [defaults] section to ensure the system will use the SHA-512 algorithm for password hashing:
crypt_style = sha512
Using a stronger hashing algorithm makes password cracking attacks more difficult.
Req-8.2.1 Set Password Hashing Algorithm in /etc/pam.d/system-auth In /etc/pam.d/system-auth, the password section of the file controls which PAM modules execute during a password change. Set the pam_unix.so module in the password section to include the argument sha512, as shown below:
password    sufficient    pam_unix.so sha512 other arguments...
This will help ensure when local users change their passwords, hashes for the new passwords will be generated using the SHA-512 algorithm. This is the default.
Using a stronger hashing algorithm makes password cracking attacks more difficult.
Req-8.2.5 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.
Req-8.1.6 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.
Req-8.2.3 Set Password Minimum Length The pam_cracklib module's minlen parameter controls requirements for minimum characters required in a password. Add minlen= after pam_pwquality to set minimum password length requirements. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to exponentially increase the time and/or resources required to compromise the password.
Req-8.2.3 Set Password Strength Minimum Digit Characters The pam_cracklib module's dcredit parameter controls requirements for usage of digits in a password. When set to a negative number, any password will be required to contain that many digits. When set to a positive number, pam_cracklib will grant +1 additional length credit for each digit. Add dcredit=-1 after pam_cracklib.so to require use of a digit in passwords. Requiring digits makes password guessing attacks more difficult by ensuring a larger search space.
Req-8.2.3 Set Password Strength Minimum Lowercase Characters The pam_cracklib module's lcredit= parameter controls requirements for usage of lowercase letters in a password. When set to a negative number, any password will be required to contain that many lowercase characters. When set to a positive number, pam_cracklib will grant +1 additional length credit for each lowercase character. Add lcredit=-1 after pam_cracklib.so to require use of a lowercase character in passwords. Requiring a minimum number of lowercase characters makes password guessing attacks more difficult by ensuring a larger search space.
Req-8.2.3 Set Password Strength Minimum Uppercase Characters The pam_cracklib module's ucredit= parameter controls requirements for usage of uppercase letters in a password. When set to a negative number, any password will be required to contain that many uppercase characters. When set to a positive number, pam_cracklib will grant +1 additional length credit for each uppercase character. Add ucredit=-1 after pam_cracklib.so to require use of an upper case character in passwords. Requiring a minimum number of uppercase characters makes password guessing attacks more difficult by ensuring a larger search space.
Req-10.2.4 Set Last Login/Access Notification To configure the system to notify users of last login/access using pam_lastlog, add the following line immediately after session required pam_limits.so:
session       required     pam_lastlog.so showfailed
Users need to be aware of activity that occurs regarding their account. Providing users with information regarding the number of unsuccessful attempts that were made to login to their account allows the user to determine if any unauthorized activity has occurred and gives them an opportunity to notify administrators.
Req-8.1.1 Ensure All Accounts on the System Have Unique Names Change usernames, or delete accounts, so each has a unique name. Unique usernames allow for accountability on the system.
Req-8.1.4 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. 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.
Req-8.2.4 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.
Setting the password maximum age ensures users are required to periodically change their passwords. This could possibly decrease the utility of a stolen password. Requiring shorter password lifetimes increases the risk of users writing down the password in a convenient location subject to physical compromise.
Req-8.2.3 Prevent Log In 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 onto 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.
Req-8.2.1 Verify All Account Password Hashes are Shadowed If any password hashes are stored in /etc/passwd (in the second field, instead of an x), the cause of this misconfiguration should be investigated. The account should have its password reset and the hash should be properly stored, or the account should be deleted entirely. The hashes for all user account passwords should be stored in the file /etc/shadow and never in /etc/passwd, which is readable by all users.
Req-8.5.a 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. Inconsistency in GIDs between /etc/passwd and /etc/group could lead to a user having unintended rights.
Req-8.7.c 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.
Req-8.7.c 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.
Req-8.7.c Verify Permissions on group File To properly set the permissions of /etc/group, run the command:
$ sudo chmod 644 /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.
Req-8.7.c 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.
Req-8.7.c 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.
Req-8.7.c 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.
Req-8.7.c 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.
Req-8.7.c 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.
Req-8.7.c 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.
Req-10.5.3 Configure auditd to use audispd's syslog plugin To configure the auditd service to use the syslog plug-in of the audispd audit event multiplexor, set the active line in /etc/audisp/plugins.d/syslog.conf to yes. Restart the auditd service:
$ sudo service auditd restart
The auditd service does not include the ability to send audit records to a centralized server for management directly. It does, however, include a plug-in for audit event multiplexor (audispd) to pass audit records to the local syslog server
Req-10.7.a 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.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - fchown At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S fchown -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S fchown -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - setxattr At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S setxattr -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S setxattr -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - fsetxattr At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S fsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S fsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - chown At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S chown -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S chown -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - fchownat At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S fchownat -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S fchownat -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - chmod At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S chmod -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S chmod  -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - fchmodat At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S fchmodat -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S fchmodat -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - removexattr At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S removexattr -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S removexattr -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - fremovexattr At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S fremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S fremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - lsetxattr At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S lsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S lsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - fchmod At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S fchmod -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S fchmod -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - lremovexattr At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S lremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S lremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.5.5 Record Events that Modify the System's Discretionary Access Controls - lchown At a minimum the audit system should collect file permission changes for all users and root. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod
The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.
Req-10.4.2.b Record Attempts to Alter the localtime File Add the following to /etc/audit/audit.rules:
-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.
Req-10.4.2.b Record attempts to alter time through settimeofday On a 32-bit system, add the following to /etc/audit/audit.rules:
# audit_time_rules
-a always,exit -F arch=b32 -S settimeofday -k audit_time_rules
On a 64-bit system, add the following to /etc/audit/audit.rules:
# audit_time_rules
-a always,exit -F arch=b64 -S settimeofday -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. 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 -S settimeofday -k 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.
Req-10.4.2.b Record Attempts to Alter Time Through stime Add the following line to /etc/audit/audit.rules for both 32-bit and 64-bit systems:
# audit_time_rules
-a always,exit -F arch=b32 -S stime -k 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 syscalls:
-a always,exit -F arch=b64 -S adjtimex -S settimeofday -k 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.
Req-10.4.2.b Record Attempts to Alter Time Through clock_settime On a 32-bit system, add the following to /etc/audit/audit.rules:
# time-change
-a always,exit -F arch=b32 -S clock_settime -F a0=0x0 -F key=time-change
On a 64-bit system, add the following to /etc/audit/audit.rules:
# time-change
-a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -F key=time-change
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 -S settimeofday -k 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.
Req-10.4.2.b Record attempts to alter time through adjtimex On a 32-bit system, add the following to /etc/audit/audit.rules:
# audit_time_rules
-a always,exit -F arch=b32 -S adjtimex -k audit_time_rules
On a 64-bit system, add the following to /etc/audit/audit.rules:
# audit_time_rules
-a always,exit -F arch=b64 -S adjtimex -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. 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 -S settimeofday -k 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.
Req-10.2.7 Ensure auditd Collects Information on Kernel Module Loading and Unloading Add the following to /etc/audit/audit.rules in order to capture kernel module loading and unloading events, setting ARCH to either b32 or b64 as appropriate for your system:
-w /sbin/insmod -p x -k modules
-w /sbin/rmmod -p x -k modules
-w /sbin/modprobe -p x -k modules
-a always,exit -F arch=ARCH -S init_module -S delete_module -k modules
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.
Req-10.2.2 Ensure auditd Collects File Deletion Events by User At a minimum the audit system should collect file deletion events for all users and root. Add the following to /etc/audit/audit.rules, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir -S unlink -S unlinkat -S rename -S renameat -F auid>=500 -F auid!=4294967295 -k 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.
Req-10.2.5.b Ensure auditd Collects File Deletion Events by User At a minimum the audit system should collect file deletion events for all users and root. Add the following to /etc/audit/audit.rules, setting ARCH to either b32 or b64 as appropriate for your system:
-a always,exit -F arch=ARCH -S rmdir -S unlink -S unlinkat -S rename -S renameat -F auid>=500 -F auid!=4294967295 -k 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.
Req-10.2.2 Ensure auditd Collects System Administrator Actions At a minimum the audit system should collect administrator actions for all users and root. Add the following to /etc/audit/audit.rules:
-w /etc/sudoers -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.
Req-10.2.5.b Ensure auditd Collects System Administrator Actions At a minimum the audit system should collect administrator actions for all users and root. Add the following to /etc/audit/audit.rules:
-w /etc/sudoers -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.
Req-10.5.5 Record Events that Modify the System's Network Environment Add the following to /etc/audit/audit.rules, setting ARCH to either b32 or b64 as appropriate for your system:
# audit_rules_networkconfig_modification
-a always,exit -F arch=ARCH -S sethostname -S setdomainname -k 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.
Req-10.2.2 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
Then, for each setuid / setgid program on the system, add a line of the following form to /etc/audit/audit.rules, where SETUID_PROG_PATH is the full path to each setuid / setgid program in the list:
-a always,exit -F path=SETUID_PROG_PATH -F perm=x -F auid>=500 -F auid!=4294967295 -k privileged
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.
Req-10.2.3 Record Attempts to Alter Process and Session Initiation Information The audit system already collects process information for all users and root. To watch for attempted manual edits of files involved in storing such process information, add the following to /etc/audit/audit.rules:
-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.
Req-10.2.7 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. Add the following to /etc/audit/audit.rules, 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!=4294967295 -k 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.
Req-10.2.4 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. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k access
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k 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.
Req-10.2.1 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. Add the following to /etc/audit/audit.rules:
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k access
If the system is 64 bit then also add the following:
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
-a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k 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.
Req-10.5.1 System Audit Logs Must Be Owned By Root To properly set the owner of /var/log, run the command:
$ sudo chown root /var/log 
Failure to give ownership of the audit log files to root allows the designated owner, and unauthorized users, potential access to sensitive information.
Req-10.2.5 Record Events that Modify User/Group Information Add the following to /etc/audit/audit.rules, in order to capture events that modify account changes:
# audit_rules_usergroup_modification
-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.
Req-10.5.2 Make the auditd Configuration Immutable Add the following to /etc/audit/audit.rules in order to make the 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
Req-10.5.5 Record Events that Modify the System's Mandatory Access Controls Add the following to /etc/audit/audit.rules:
-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.
Req-8.1.8 Implement Blank Screensaver Run the following command to set the screensaver mode in the GNOME desktop to a blank screen:
$ sudo gconftool-2 --direct \
  --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
  --type string \
  --set /apps/gnome-screensaver/mode blank-only
Setting the screensaver mode to blank-only conceals the contents of the display from passersby.
Req-8.1.8 Enable Screen Lock Activation After Idle Period Run the following command to activate locking of the screensaver in the GNOME desktop when it is activated:
$ sudo gconftool-2 --direct \
  --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
  --type bool \
  --set /apps/gnome-screensaver/lock_enabled true
Enabling the activation of the screen lock after an idle period ensures password entry will be required in order to access the system, preventing access by passersby.
Req-8.1.8 GNOME Desktop Screensaver Mandatory Use Run the following command to activate the screensaver in the GNOME desktop after a period of inactivity:
$ sudo gconftool-2 --direct \
  --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
  --type bool \
  --set /apps/gnome-screensaver/idle_activation_enabled true
Enabling idle activation of the screensaver ensures the screensaver will be activated after the idle delay. Applications requiring continuous, real-time screen display (such as network management products) require the login session does not have administrator rights and the display station is located in a controlled-access area.
Req-8.1.8 Set GNOME Login Inactivity Timeout Run the following command to set the idle time-out value for inactivity in the GNOME desktop to minutes:
$ sudo gconftool-2 \
  --direct \
  --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
  --type int \
  --set /desktop/gnome/session/idle_delay 
Setting the idle delay controls when the screensaver will start, and can be combined with screen locking to prevent access from passersby.
Req-4.1 Install openswan or libreswan Package The openswan and libreswan packages provide an implementation of IPsec and IKE, which permits the creation of secure tunnels over untrusted networks. The openswan package can be installed with the following command:
$ sudo yum install openswan
The libreswan package can be installed with the following command:
$ sudo yum install libreswan
Providing the ability for remote users or systems to initiate a secure VPN connection protects information when it is transmitted over a wide area network.
Req-6.2 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
Ensuring the validity of packages' cryptographic signatures prior to installation ensures the authenticity of the software and protects against malicious tampering.
Req-6.2 Ensure Software Patches Installed If the system is joined to the Red Hat Network, a Red Hat Satellite Server, or a yum server, run the following command to install updates:
$ sudo yum update
If the system is not configured to use one of these sources, updates (in the form of RPM packages) can be manually downloaded from the Red Hat Network and installed using rpm.
Installing software updates is a fundamental mitigation against the exploitation of publicly-known vulnerabilities.
Req-6.2 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
The Red Hat GPG key is necessary to cryptographically verify packages are from Red Hat.
Req-6.2 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
Ensuring all packages' cryptographic signatures are valid prior to installation ensures the authenticity of the software and protects against malicious tampering.
Req-7.1 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.
Req-7.1 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.
Req-8.3 Enable Smart Card Login To enable smart card authentication, consult the documentation at: For guidance on enabling SSH to authenticate against a Common Access Card (CAC), consult documentation at: Smart card login provides two-factor authentication stronger than that provided by a username and password combination. Smart cards leverage PKI (public key infrastructure) in order to provide and verify credentials.
Req-10 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
Ensuring the auditd service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.
Req-10.3 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.
Req-10.4 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
Req-10.5 System Audit Logs Must Have Mode 0640 or Less Permissive If log_group in /etc/audit/auditd.conf is set to a group other than the root group account, change the mode of the audit log files with the following command:
$ sudo chmod 0640 audit_file

Otherwise, change the mode of the audit log files with the following command:
$ sudo chmod 0600 audit_file
If users can write to audit logs, audit trails can be modified or destroyed.
Req-10.7 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.
Req-10.7 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.
Req-10.7 Configure auditd space_left 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 SIZE_in_MB appropriately:
space_left = SIZE_in_MB
Set this value to the appropriate size in Megabytes cause the system to notify the user of an issue.
Notifying administrators of an impending disk space problem may allow them to take corrective action prior to any disruption.
Req-10.7 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:
  • ignore
  • 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.
Req-10.7 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.
Req-10.7 Configure auditd Number of Logs Retained Determine how many log files auditd should retain when it rotates logs. Edit the file /etc/audit/auditd.conf. Add or modify the following line, substituting NUMLOGS with the correct value of :
num_logs = NUMLOGS
Set the value to 5 for general-purpose systems. Note that values less than 2 result in no log rotation.
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.
Req-10.7 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:
  • ignore
  • 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.
Req-11.4 Install Intrusion Detection Software The base Red Hat platform already includes a sophisticated auditing system that can detect intruder activity, as well as SELinux, which provides host-based intrusion prevention capabilities by confining privileged programs and user sessions which may become compromised.
In DoD environments, supplemental intrusion detection tools, such as, the McAfee Host-based Security System, are available to integrate with existing infrastructure. When these supplemental tools interfere with the proper functioning of SELinux, SELinux takes precedence.
Host-based intrusion detection tools provide a system-level defense when an intruder gains access to a system or network.
Req-11.5 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. After locating a file with incorrect permissions which can be found with
$ rpm -Va | grep '^.M'
, 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.
Req-11.5 Verify File Hashes with RPM The RPM package management system can check the hashes of installed software packages, including many that are important to system security. 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.
Req-11.5 Install AIDE Install the AIDE package with the command:
$ sudo yum install aide
The AIDE package must be installed if it is to be available for integrity checking.
Req-11.5 Configure Periodic Execution of AIDE 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
AIDE can be executed periodically through other means; this is merely one example.
By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.
Req-11.5 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.
Req-11.5 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.