6.3.3.6 Ensure events that modify /etc/issue and /etc/issue.net are collected

Information

Record changes to network environment files or system calls. The files being monitored are:

- /etc/issue and /etc/issue.net - messages displayed pre-login

Monitoring /etc/issue and /etc/issue.net is important, as intruders could put disinformation into those files and trick users into providing information to the intruder.

Solution

Note:

- The -w option is deprecated and the rule should be updated in accordance with the Remediation Procedure.
- For best performance, the arch field should be supplied in the rule. The individual permissions will cause the selection of specific system calls that use that kind of access. Not supplying the arch will cause the selection of all system calls which will affect performance as all system calls will be evaluated.

- Edit or create a file in the /etc/audit/rules.d/ directory, ending inrules extension, with the relevant rules to monitor events that modify the system's network environment.

Example :

# printf "
-a always,exit -F arch=b64 -S all -F path=/etc/issue -F perm=wa -F key=system-locale
-a always,exit -F arch=b64 -S all -F path=/etc/issue.net -F perm=wa -F key=system-locale
" >> /etc/audit/rules.d/50-etc_issue_system_locale.rules <xhtml:ol start="2"> - Merge and load the rules into active configuration:

# augenrules --load <xhtml:ol start="3"> - Check if reboot is required:

# if [[ $(auditctl -s | grep "enabled") =~ "2" ]]; then printf "Reboot required to load rules\n"; fi

See Also

https://workbench.cisecurity.org/benchmarks/23593