name: Linux Edit Cron Table Parameter
id: 0d370304-5f26-11ec-a4bb-acde48001122
version: 1
date: '2021-12-17'
author: Teoderick Contreras, Splunk
type: Hunting
datamodel:
- Endpoint
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.
search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
  as lastTime from datamodel=Endpoint.Processes where Processes.process_name = crontab
  Processes.process = "*crontab *" Processes.process = "* -e*" by Processes.dest Processes.user
  Processes.parent_process_name Processes.process_name Processes.process Processes.process_id
  Processes.parent_process_id | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)` | `linux_edit_cron_table_parameter_filter`'
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
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1053.003/crontab_edit_parameter/sysmon_linux.log
  kill_chain_phases:
  - Privilege Escalation
  mitre_attack_id:
  - T1053.003
  - T1053
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Processes.dest
  - Processes.user
  - Processes.parent_process_name
  - Processes.process_name
  - Processes.process
  - Processes.process_id
  - Processes.parent_process_id
  security_domain: endpoint
  impact: 30
  confidence: 30
  risk_score: 9
  context:
  - Source:Endpoint
  - Stage:Privilege Escalation
  - Stage:Persistence
  message: A possible crontab edit command $process$ executed on $dest$
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  nist:
  - DE.CM
  cis20:
  - CIS 3
  - CIS 5
  - CIS 16
  automated_detection_testing: passed