Linux Restricted Shell Breakout via awk Commands

Identifies Linux binary awk abuse to breakout out of restricted shells or environments by spawning an interactive system shell. The awk utility is a text processing language used for data extraction and reporting tools 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 (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://gtfobins.github.io/gtfobins/nawk/
• https://gtfobins.github.io/gtfobins/mawk/

Tags:

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

Version: 1

Rule authors:

• Elastic

Rule license: Elastic License v2

process where event.type == "start" and process.name in ("sh", "bash", "dash") and
  process.parent.name in ("nawk", "mawk", "awk", "gawk") and process.parent.args : "BEGIN {system(*)}"

Framework: 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/

• Sub-technique:

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