name: Linux Edit Cron Table Parameter
id: 0d370304-5f26-11ec-a4bb-acde48001122
version: 1
date: '2021-12-17'
author: Teoderick Contreras, Splunk
status: production
type: Hunting
description: 'The following analytic detects the suspicious editing of cron jobs in
  Linux via the crontab command-line parameter. This tactic could be used by adversaries
  or malware to schedule execution of their malicious code, potentially leading to
  system compromise or unauthorized persistent access. It pinpoints this activity
  by monitoring command-line executions involving ''crontab'' and the edit parameter
  (-e).\

  Recognizing such activity is vital for a SOC as cron job manipulations might signal
  unauthorized persistence attempts or scheduled malicious actions, potentially resulting
  in substantial harm. A true positive signifies an active threat, with implications
  ranging from unauthorized access to broader network compromise.\

  To implement this analytic, logs capturing process name, parent process, and command-line
  executions from your endpoints must be ingested.\

  Known false positives could stem from valid administrative tasks or automation processes
  using crontab. To reduce these, fine-tune the filter macros according to the benign
  activities within your environment. These adjustments ensure legitimate actions
  aren''t mistaken for threats, allowing analysts to focus on genuine potential risks.\'
data_source:
- Sysmon Event ID 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.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: 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/
tags:
  analytic_story:
  - Linux Privilege Escalation
  - Linux Persistence Techniques
  - Linux Living Off The Land
  - Scheduled Tasks
  asset_type: Endpoint
  confidence: 30
  impact: 30
  message: A possible crontab edit command $process$ executed on $dest$
  mitre_attack_id:
  - T1053.003
  - T1053
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  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
  risk_score: 9
  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