Linux Restricted Shell Breakout via env Shell Evasionedit

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 operating systems and is used to print a list of environment variables. The activity of spawning a 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:

Tags:

  • Elastic
  • Host
  • Linux
  • Threat Detection
  • Execution
  • GTFOBins

Version: 2

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule queryedit

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&CKTM