linux_auditd_edit_cron_table_parameter.yml

name: Linux Auditd Edit Cron Table Parameter
id: f4bb7321-7e64-4d1e-b1aa-21f8b019a91f
version: 6
date: '2025-05-02'
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/
drilldown_searches:
- name: View the detection results for - "$dest$"
  search: '%original_detection_search% | search  dest = "$dest$"'
  earliest_offset: $info_min_time$
  latest_offset: $info_max_time$
- name: View risk events for the last 7 days for - "$dest$"
  search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$")
    starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime
    values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories)
    as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic)
    as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`'
  earliest_offset: $info_min_time$
  latest_offset: $info_max_time$
rba:
  message: A SYSCALL - [$comm$] event was executed on host - [$dest$] to edit the
    cron table.
  risk_objects:
  - field: dest
    type: system
    score: 64
  threat_objects: []
tags:
  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
  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/linux_auditd_crontab_edit_new/linux_auditd_new_crontab.log
    source: auditd
    sourcetype: auditd