Linux Adding Crontab Using List Parameter

name: Linux Adding Crontab Using List Parameter
id: 52f6d751-1fd4-4c74-a4c9-777ecfeb5c58
version: 11
creation_date: '2021-12-21'
modification_date: '2026-05-13'
author: Teoderick Contreras, Bhavin Patel, Splunk
status: production
type: Hunting
description: The following analytic detects suspicious modifications to cron jobs on Linux systems using the crontab command with list parameters. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and command-line executions. This activity is significant as it may indicate an attempt to establish persistence or execute malicious code on a schedule. If confirmed malicious, the impact could include unauthorized code execution, data destruction, or other damaging outcomes. Further investigation should analyze the added cron job, its associated command, and any related processes.
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= "* -l*"
      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_adding_crontab_using_list_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://www.welivesecurity.com/2022/04/12/industroyer2-industroyer-reloaded/
    - https://cert.gov.ua/article/39518
analytic_story:
    - Cisco Isovalent Suspicious Activity
    - Industroyer2
    - Linux Privilege Escalation
    - Linux Living Off The Land
    - Data Destruction
    - Linux Persistence Techniques
    - Scheduled Tasks
    - Gomir
    - VoidLink Cloud-Native Linux Malware
asset_type: Endpoint
mitre_attack_id:
    - T1053.003
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
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_list_parameter/sysmon_linux.log
          source: Syslog:Linux-Sysmon/Operational
          sourcetype: sysmon:linux
      test_type: unit
    - name: True Positive Test - Cisco Isovalent
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/cisco_isovalent/cisco_isovalent.log
          source: not_applicable
          sourcetype: cisco:isovalent:processExec
      test_type: unit