name: GitHub Pull Request from Unknown User
id: 9d7b9100-8878-4404-914e-ca5e551a641e
version: 1
date: '2021-09-01'
author: Patrick Bareiss, Splunk
status: production
type: Anomaly
description: The following analytic detects pull requests from unknown users on GitHub. The detection is made by using a Splunk query to search for pull requests in the `check_suite.pull_requests` field where the `id` is not specified. Next, the analytic retrieves information such as the author's name, the repository's full name, the head reference of the pull request, and the commit message from the `check_suite.head_commit` field. The analytic also includes a step to exclude known users by using the `github_known_users` lookup table, which helps to filter out pull requests from known users and focus on the pull requests from unknown users. The detection is important because it locates potential malicious activity or unauthorized access since unknown users can introduce malicious code or gain unauthorized access to repositories leading to unauthorized code changes, data breaches, or other security incidents. Next steps include reviewing the author's name, the repository involved, the head reference of the pull request, and the commit message upon triage of a potential pull request from an unknown user. You must also analyze any relevant on-disk artifacts and investigate any concurrent processes to determine the source and intent of the pull request."
data_source: []
search: '`github` check_suite.pull_requests{}.id=* | stats count by check_suite.head_commit.author.name
  repository.full_name check_suite.pull_requests{}.head.ref check_suite.head_commit.message
  | rename check_suite.head_commit.author.name as user repository.full_name as repository
  check_suite.pull_requests{}.head.ref as ref_head check_suite.head_commit.message
  as commit_message | search NOT `github_known_users` | eval phase="code" | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)` | `github_pull_request_from_unknown_user_filter`'
how_to_implement: You must index GitHub logs. You can follow the url in reference
  to onboard GitHub logs.
known_false_positives: unknown
references:
- https://www.splunk.com/en_us/blog/tips-and-tricks/getting-github-data-with-webhooks.html
tags:
  analytic_story:
  - Dev Sec Ops
  asset_type: GitHub
  confidence: 90
  impact: 30
  message: Vulnerabilities found in packages used by GitHub repository $repository$
  mitre_attack_id:
  - T1195.001
  - T1195
  observable:
  - name: repository
    type: Unknown
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - alert.id
  - repository.full_name
  - repository.html_url
  - action
  - alert.affected_package_name
  - alert.affected_range
  - alert.created_at
  - alert.external_identifier
  - alert.external_reference
  - alert.fixed_in
  - alert.severity
  risk_score: 27
  security_domain: network
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1195.001/github_pull_request/github_pull_request.json
    sourcetype: aws:firehose:json
    source: github