Linux Process Creation: crontab -l Enumeration

Flags Linux executions of /crontab with the -l option to list a user’s scheduled cron tasks.

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linux-process-creation-crontab-l-enumeration-403ed92c

title: "Linux Process Creation: crontab -l Enumeration"
id: 01062ca0-9d06-4a1d-8721-07e1395aa403
status: test
description: This rule matches Linux process executions where the binary path ends with /crontab and the command line includes the -l option. Attackers and operators may use this to enumerate a user's scheduled tasks as part of discovery and situational awareness. The detection relies on process creation telemetry, specifically the executable path and command-line arguments.
references:
  - https://blogs.jpcert.or.jp/en/2023/05/gobrat.html
  - https://jstnk9.github.io/jstnk9/research/GobRAT-Malware/
  - https://www.virustotal.com/gui/file/60bcd645450e4c846238cf0e7226dc40c84c96eba99f6b2cffcd0ab4a391c8b3/detection
  - https://www.virustotal.com/gui/file/3e44c807a25a56f4068b5b8186eee5002eed6f26d665a8b791c472ad154585d1/detection
  - https://github.com/SigmaHQ/sigma/blob/master/rules/linux/process_creation/proc_creation_lnx_crontab_enumeration.yml
author: Joseliyo Sanchez, @Joseliyo_Jstnk, Huntrule Team
date: 2023-06-02
tags:
  - attack.discovery
  - attack.t1007
logsource:
  product: linux
  category: process_creation
detection:
  selection:
    Image|endswith: /crontab
    CommandLine|contains: " -l"
  condition: selection
falsepositives:
  - Legitimate use of crontab
level: low
license: DRL-1.1
related:
  - id: 403ed92c-b7ec-4edd-9947-5b535ee12d46
    type: derived

What it detects

This rule matches Linux process executions where the binary path ends with /crontab and the command line includes the -l option. Attackers and operators may use this to enumerate a user's scheduled tasks as part of discovery and situational awareness. The detection relies on process creation telemetry, specifically the executable path and command-line arguments.

Known false positives

Legitimate use of crontab

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.