Linux Restricted Shell Breakout via env Shell Evasion

Identifies Linux binary env abuse to break out from restricted environments by spawning an interactive system shell.The env utility is a shell command for Unix like OS which is used to print a list of environment variables and the activity of spawning shell is not a standard use of this binary for a user or system administrator. It indicates a potentially 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: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://gtfobins.github.io/gtfobins/env/

Tags:

Elastic
Host
Linux
Threat Detection
Execution
GTFOBins

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

process where event.type == "start" and process.name : "env" and process.args_count == 2 and process.args : ("/bin/sh", "/bin/bash", "sh", "bash")

Framework: MITRE ATT&CK^TM

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/
Sub-technique:
- Name: Unix Shell
- ID: T1059.004
- Reference URL: https://attack.mitre.org/techniques/T1059/004/

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