InformationCapture events where the system date and/or time has been modified. The parameters in this section are set to determine if the;
adjtimex - tune kernel clock
settimeofday - set time using timeval and timezone structures
stime - using seconds since 1/1/1970
clock_settime - allows for the setting of several internal clocks and timers
system calls have been executed. Further, ensure to write an audit record to the configured audit log file upon exit, tagging the records with a unique identifier such as 'time-change'.
Unexpected changes in system date and/or time could be a sign of malicious activity on the system.
SolutionCreate audit rules
Edit or create a file in the /etc/audit/rules.d/ directory, ending in .rules extension, with the relevant rules to monitor events that modify date and time information.
64 Bit systems
# printf '
-a always,exit -F arch=b64 -S adjtimex,settimeofday,clock_settime -k time-change
-a always,exit -F arch=b32 -S adjtimex,settimeofday,clock_settime -k time-change
-w /etc/localtime -p wa -k time-change
' >> /etc/audit/rules.d/50-time-change.rules
Load audit rules
Merge and load the rules into active configuration:
# augenrules --load
Check if reboot is required.
# if [[ $(auditctl -s | grep 'enabled') =~ '2' ]]; then printf 'Reboot required to load rules
32 Bit systems
Follow the same procedures as for 64 bit systems and ignore any entries with b64. In addition, add stime to the system call audit. Example:
-a always,exit -F arch=b32 -S adjtimex,settimeofday,clock_settime,stime -k time-change
Potential reboot required
If the auditing configuration is locked (-e 2), then augenrules will not warn in any way that rules could not be loaded into the running configuration. A system reboot will be required to load the rules into the running configuration.
System call structure
For performance (man 7 audit.rules) reasons it is preferable to have all the system calls on one line. However, your configuration may have them on one line each or some other combination. This is important to understand for both the auditing and remediation sections as the examples given are optimised for performance as per the man page.