Detection: GitHub Enterprise Delete Branch Ruleset

Updated Date: 2025-01-17 ID: 6169ea23-3719-439f-957a-0ea5174b70e2 Author: Patrick Bareiss, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

The following analytic detects when branch rules are deleted in GitHub Enterprise. The detection monitors GitHub Enterprise audit logs for branch rule deletion events by tracking actor details, repository information, and associated metadata. For a SOC, identifying deleted branch rules is critical as it could indicate attempts to bypass code review requirements and security controls. Branch deletion rules are essential security controls that enforce code review, prevent force pushes, and maintain code quality. Disabling these protections could allow malicious actors to directly push unauthorized code changes or backdoors to protected branches. The impact of disabled branch protection includes potential code tampering, bypass of security reviews, introduction of vulnerabilities or malicious code, and compromise of software supply chain integrity. This activity could be part of a larger attack chain where an adversary first disables security controls before attempting to inject malicious code.

1`github_enterprise` action=repository_ruleset.destroy 
2| fillnull 
3| stats count min(_time) as firstTime max(_time) as lastTime by actor, actor_id, actor_ip, actor_is_bot, actor_location.country_code, business, business_id, org, org_id, repo, repo_id, user_agent, action, ruleset_name 
4| eval user=actor 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `github_enterprise_delete_branch_ruleset_filter`

Data Source

Name Platform Sourcetype Source
GitHub Enterprise Audit Logs N/A 'httpevent' 'http:github'

Macros Used

Name Value
github_enterprise source=http:github sourcetype=httpevent
github_enterprise_delete_branch_ruleset_filter search *
github_enterprise_delete_branch_ruleset_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1562.001 Disable or Modify Tools Defense Evasion
T1195 Supply Chain Compromise Initial Access
Delivery
Exploitation
DE.AE
CIS 13

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Risk Event True
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

You must ingest GitHub Enterprise logs using Audit log streaming as described in this documentation 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-streaming-to-splunk using a Splunk HTTP Event Collector.

Known False Positives

unknown

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

$user$ deleted a branch ruleset in repo $repo$

Risk Object Risk Object Type Risk Score Threat Objects
user user 25 user_agent

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset http:github httpevent
Integration ✅ Passing Dataset http:github httpevent

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 1