Linux Auditd Edit Cron Table Parameter

name: Linux Auditd Edit Cron Table Parameter
id: f4bb7321-7e64-4d1e-b1aa-21f8b019a91f
version: 10
creation_date: '2024-08-12'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
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:
    - Linux Auditd Syscall
search: |-
    `linux_auditd` type=SYSCALL syscall IN ("rename", "execve") (comm IN ("crontab") OR exe IN ("*/crontab")) success=yes AND NOT (UID IN("daemon"))
      | rename host as dest
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY comm exe syscall
           uid ppid pid
           dest
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `linux_auditd_edit_cron_table_parameter_filter`
how_to_implement: To implement this detection, the process begins by ingesting auditd data, that consist SYSCALL, TYPE, EXECVE and PROCTITLE events, which captures command-line executions and process details on Unix/Linux systems. These logs should be ingested and processed using Splunk Add-on for Unix and Linux (https://splunkbase.splunk.com/app/833), which is essential for correctly parsing and categorizing the data. The next step involves normalizing the field names  to match the field names set by the Splunk Common Information Model (CIM) to ensure consistency across different data sources and enhance the efficiency of data modeling. This approach enables effective monitoring and detection of linux endpoints where auditd is deployed
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/
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: A SYSCALL - [$comm$] event was executed on host - [$dest$] to edit the cron table.
analytic_story:
    - Scheduled Tasks
    - Linux Privilege Escalation
    - Linux Persistence Techniques
    - Linux Living Off The Land
    - Compromised Linux Host
asset_type: Endpoint
mitre_attack_id:
    - T1053.003
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint