Suspicious CronTab Creation or Modification

Elastic Stack Serverless Security

Identifies attempts to create or modify a crontab via a process that is not crontab (i.e python, osascript, etc.). This activity should not be highly prevalent and could indicate the use of cron as a persistence mechanism by a threat actor.

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://taomm.org/PDFs/vol1/CH%200x02%20Persistence.pdf
• https://theevilbit.github.io/beyond/beyond_0004/

Tags:

• Elastic
• Host
• macOS
• Threat Detection
• Persistence

Version: 101

Rule authors:

• Elastic

Rule license: Elastic License v2

file where event.type != "deletion" and process.name != null and
  file.path : "/private/var/at/tabs/*" and not process.executable == "/usr/bin/crontab"

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Persistence
  • ID: TA0003
  • Reference URL: https://attack.mitre.org/tactics/TA0003/

• Technique:

  • Name: Scheduled Task/Job
  • ID: T1053
  • Reference URL: https://attack.mitre.org/techniques/T1053/

• Sub-technique:

  • Name: Cron
  • ID: T1053.003
  • Reference URL: https://attack.mitre.org/techniques/T1053/003/