Github Outside Collaborator Detected — Sigma Rule

Rule metadata and linked tags

Author: Muhammad Faisal (@faisalusuf). Source status: test; severity: medium. Source dates: 2023-01-20 / not supplied.

{
  "product": "github",
  "service": "audit",
  "definition": "Requirements: The audit log streaming feature must be enabled to be able to receive such logs. You can enable following the documentation here: https://docs.github.com/en/enterprise-cloud@latest/admin/monitoring-activity-in-your-enterprise/reviewing-audit-logs-for-your-enterprise/streaming-the-audit-log-for-your-enterprise#setting-up-audit-log-streaming"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 84feb937cafe75cbcf92931d0ef17cb8735653b99a201f60d99acffc200cab78

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Github Outside Collaborator Detected
id: eaa9ac35-1730-441f-9587-25767bde99d7
status: test
description: |
    Detects when an organization member or an outside collaborator is added to or removed from a project board or has their permission level changed or when an owner removes an outside collaborator from an organization or when two-factor authentication is required in an organization and an outside collaborator does not use 2FA or disables 2FA.
author: Muhammad Faisal (@faisalusuf)
date: 2023-01-20
references:
    - https://docs.github.com/en/organizations/keeping-your-organization-secure/managing-security-settings-for-your-organization/reviewing-the-audit-log-for-your-organization#audit-log-actions
    - https://docs.github.com/en/organizations/keeping-your-organization-secure/managing-two-factor-authentication-for-your-organization/requiring-two-factor-authentication-in-your-organization
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.collection
    - attack.t1098.001
    - attack.t1098.003
    - attack.t1213.003
logsource:
    product: github
    service: audit
    definition: 'Requirements: The audit log streaming feature must be enabled to be able to receive such logs. You can enable following the documentation here: https://docs.github.com/en/enterprise-cloud@latest/admin/monitoring-activity-in-your-enterprise/reviewing-audit-logs-for-your-enterprise/streaming-the-audit-log-for-your-enterprise#setting-up-audit-log-streaming'
detection:
    selection:
        action:
            - 'org.remove_outside_collaborator'
            - 'project.update_user_permission'
    condition: selection
falsepositives:
    - Validate the actor if permitted to access the repo.
    - Validate the Multifactor Authentication changes.
level: medium

Original YAML and metadata in JSON

False positives

• Validate the actor if permitted to access the repo.
• Validate the Multifactor Authentication changes.

Source references

• https://docs.github.com/en/organizations/keeping-your-organization-secure/managing-security-settings-for-your-organization/reviewing-the-audit-log-for-your-organization#audit-log-actions
• https://docs.github.com/en/organizations/keeping-your-organization-secure/managing-two-factor-authentication-for-your-organization/requiring-two-factor-authentication-in-your-organization