Linux Restricted Shell Breakout via cpulimit Shell Evasion
editLinux Restricted Shell Breakout via cpulimit Shell Evasion
editIdentifies Linux binary cpulimit abuse to break out from restricted environments by spawning an interactive system shell. The cpulimit utility is used to restrict the CPU usage of a process in cases of CPU or system load exceeding the defined threshold and the activity of spawning a shell is not a standard use of this binary by a user or system administrator. This can potentially indicate a malicious actor attempting to improve the capabilities or stability of their access.
Rule type: eql
Rule indices:
- logs-endpoint.events.*
Severity: medium
Risk score: 47
Runs every: 5 minutes
Searches indices from: now-9m (Date Math format, see also Additional look-back time)
Maximum alerts per execution: 100
References:
Tags:
- Elastic
- Host
- Linux
- Threat Detection
- Execution
- GTFOBins
Version: 1
Added (Elastic Stack release): 8.2.0
Rule authors: Elastic
Rule license: Elastic License v2
Rule query
editprocess where event.type == "start" and process.name in ("bash", "sh",
"dash") and process.parent.name == "cpulimit" and
process.parent.args == "-f" and process.parent.args in ("/bin/sh",
"/bin/bash", "/bin/dash", "sh", "bash", "dash")
Threat mapping
editFramework: MITRE ATT&CKTM
-
Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
-
Technique:
- Name: Command and Scripting Interpreter
- ID: T1059
- Reference URL: https://attack.mitre.org/techniques/T1059/