Linux Edit Cron Table Parameter

Name:Linux Edit Cron Table Parameter
id:0d370304-5f26-11ec-a4bb-acde48001122
version:6
date:2025-02-10
author:Teoderick Contreras, Splunk
status:production
type:Hunting
Description:The following analytic detects the suspicious editing of cron jobs in Linux using the crontab command-line parameter (-e). It identifies this activity by monitoring command-line executions involving 'crontab' and the edit parameter. This behavior is significant for a SOC as cron job manipulations can indicate unauthorized persistence attempts or scheduled malicious actions. If confirmed malicious, this activity could lead to system compromise, unauthorized access, or broader network compromise.
Data_source:

• -Sysmon for Linux EventID 1

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.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| `security_content_ctime(lastTime)`
| `linux_edit_cron_table_parameter_filter`

how_to_implement:The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
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/
drilldown_searches:
  :
tags:
  analytic_story:
    - 'Linux Privilege Escalation'
    - 'Linux Persistence Techniques'
    - 'Linux Living Off The Land'
    - 'Scheduled Tasks'
  asset_type:Endpoint
  mitre_attack_id:
    - 'T1053.003'
  product:
    - 'Splunk Enterprise'
    - 'Splunk Enterprise Security'
    - 'Splunk Cloud'
  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
manual_test:None