name: Linux Edit Cron Table Parameter
id: 0d370304-5f26-11ec-a4bb-acde48001122
version: 1
date: '2021-12-17'
author: Teoderick Contreras, Splunk
status: production
type: Hunting
description: The following analytic identifies a suspicious cronjobs modification
  using crontab edit parameter. This commandline parameter can be abuse by malware
  author, adversaries, and red red teamers to add cronjob entry to their malicious
  code to execute to the schedule they want. This event can also be executed by administrator
  or normal user for automation purposes so filter is needed.
data_source:
- Sysmon Event ID 1
search:
  selection1:
    CommandLine: '*crontab *'
    Image|endswith: crontab
  selection2:
    CommandLine: '* -e*'
  condition: selection1 and selection2
how_to_implement: To successfully implement this search, you need to be ingesting
  logs with the process name, parent process, and command-line executions from your
  endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from
  Splunkbase.
known_false_positives: Administrator or network operator can use this application
  for automation purposes. Please update the filter macros to remove false positives.
references:
- https://attack.mitre.org/techniques/T1053/003/
tags:
  analytic_story:
  - Linux Privilege Escalation
  - Linux Persistence Techniques
  - Linux Living Off The Land
  asset_type: Endpoint
  confidence: 30
  impact: 30
  message: A possible crontab edit command $process$ executed on $dest$
  mitre_attack_id:
  - T1053.003
  - T1053
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  risk_score: 9
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1053.003/crontab_edit_parameter/sysmon_linux.log
    source: Syslog:Linux-Sysmon/Operational
    sourcetype: sysmon:linux