Setuid and Setgid
Where this stands
One published detection covers this technique. Every one is unverified — no rule on Siemphony has been executed against real telemetry.
What the technique is
An adversary may abuse configurations where an application has the setuid or setgid bits set in order to get code running in a different (and possibly more privileged) user’s context. On Linux or macOS, when the setuid or setgid bits are set for an application binary, the application will run with the privileges of the owning user or group respectively. Normally an application is run in the current user’s context, regardless of which user or group owns the application. However, there are instances where programs need to be executed in an elevated context to function properly, but the user running them may not have the specific required privileges. Instead of creating an entry in the sudoers file, which must be done by root, any user can specify the setuid or setgid flag to be set for their own applications (i.e. Linux and Mac Permissions). The chmod command can set these bits with bitmasking, chmod 4777 [file] or via shorthand naming, chmod u+s [file]. This will enable the setuid bit. To enable the setgid bit, chmod 2775 and chmod g+s can be used. Adversaries can use this mechanism on their own malware to make sure they're able to execute in elevated contexts in the future. This abuse is often part of a "shell escape" or other actions to bypass an execution environment with restricted permissions. […]
Read it on attack.mitre.orgWhat MITRE says you would watch
- AN0307
Correlation of chmod operations setting setuid/setgid bits followed by privileged process execution (EUID != UID), especially from user-writable or abnormal paths.
- AN0308
Observation of chmod commands setting setuid/setgid bits, paired with launch of binaries under elevated execution context (e.g., root-owned binaries launched by unprivileged users).
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