Information
Monitor for unsuccessful attempts to access files. The following parameters are associated with system calls that control files:
- creation - creat
- opening - open openat
- truncation - truncate ftruncate
An audit log record will only be written if all of the following criteria is met for the user when trying to access a file:
- a non-privileged user (auid>=UID_MIN)
- is not a Daemon event (auid=4294967295/unset/-1)
- if the system call returned EACCES (permission denied) or EPERM (some other permanent error associated with the specific system call)
Failed attempts to open, create or truncate files could be an indication that an individual or process is trying to gain unauthorized access to the system.
Solution
Create audit rules
Edit or create a file in the /etc/audit/rules.d/ directory, ending inrules extension, with the relevant rules to monitor unsuccessful file access attempts.
Example:
# {
UID_MIN=$(awk '/^s*UID_MIN/{print $2}' /etc/login.defs)
[ -n "${UID_MIN}" ] && printf "
-a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=-EACCES -F auid>=${UID_MIN} -F auid!=unset -k access
-a always,exit -F arch=b64 -S creat,open,openat,truncate,ftruncate -F exit=-EPERM -F auid>=${UID_MIN} -F auid!=unset -k access
-a always,exit -F arch=b32 -S creat,open,openat,truncate,ftruncate -F exit=-EACCES -F auid>=${UID_MIN} -F auid!=unset -k access
-a always,exit -F arch=b32 -S creat,open,openat,truncate,ftruncate -F exit=-EPERM -F auid>=${UID_MIN} -F auid!=unset -k access
" >> /etc/audit/rules.d/50-access.rules || printf "ERROR: Variable 'UID_MIN' is unset.
"
}
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
"; fi