GitHub Outgoing Repository Transfer Initiated

Severity: high
Type: alert
Time window: 30m
Match by: github_repo_name, user_id
Author: Google Cloud Security
Source: github.com/chronicle/detection-rules

Detects when a GitHub repository is transferred.

References

https://docs.github.com/en/enterprise-cloud@latest/admin/monitoring-activity-in-your-enterprise/reviewing-audit-logs-for-your-enterprise/audit-log-events-for-your-enterprise

Telemetry coverage

Platform	Record / event type
GitHub	Audit log action `repo.transfer_outgoing`: Repository transferred to another network

Rules detecting the same action

These rules filter on the same operation.

Github Repository Transfer (Panther)
Github Repository/Organization Transferred (Sigma)

Rule body

// Copyright 2024 Google LLC. Licensed under Apache-2.0.

rule github_outgoing_repository_transfer_initiated {

  meta:
    author = "Google Cloud Security"
    description = "Detects when a GitHub repository is transferred."
    rule_id = "mr_28486f60-1be2-467c-a3e6-6105491c3226"
    rule_name = "GitHub Outgoing Repository Transfer Initiated"
    assumption = "Your GitHub enterprise audit log settings are configured to log the source IP address for events. Reference: https://docs.github.com/en/organizations/keeping-your-organization-secure/managing-security-settings-for-your-organization/displaying-ip-addresses-in-the-audit-log-for-your-organization"
    type = "alert"
    severity = "High"
    priority = "High"
    platform = "GitHub"
    data_source = "github"
    reference = "https://docs.github.com/en/enterprise-cloud@latest/admin/monitoring-activity-in-your-enterprise/reviewing-audit-logs-for-your-enterprise/audit-log-events-for-your-enterprise"

  events:
    $github.metadata.vendor_name = "GITHUB" nocase
    $github.metadata.product_name = "GITHUB"
    $github.metadata.product_event_type = "repo.transfer_outgoing"
    $github.principal.user.userid = $user_id
    $github.target.resource.name = $github_repo_name

  match:
    $user_id, $github_repo_name over 30m

  outcome:
    $risk_score = max(85)
    $event_count = count_distinct($github.metadata.id)
    $principal_ip = array_distinct($github.principal.ip)
    $principal_user_userid = array_distinct($github.principal.user.userid)
    $principal_ip_country = array_distinct($github.principal.ip_geo_artifact.location.country_or_region)
    $principal_ip_state = array_distinct($github.principal.ip_geo_artifact.location.state)
    $principal_ip_city = array_distinct($github.principal.location.city)
    $security_result_summary = array_distinct($github.security_result.summary)

  condition:
    $github
}

YARA-L rule structure

Condition

Fires when at least one $github event in the 30m window.

Events

`$github`

metadata.product_event_type = "repo.transfer_outgoing"

Match and correlation

Match key: $github_repo_name (target.resource.name), $user_id (principal.user.userid)
Within: 30m

Outcome

Outcome variables add context to a detection. When the rule generates an alert, $risk_score is displayed with it.

Field	Expression
`risk_score`	`max(85)`
`event_count`	`count_distinct($github.metadata.id)`
`principal_ip`	`array_distinct($github.principal.ip)`
`principal_user_userid`	`array_distinct($github.principal.user.userid)`
`principal_ip_country`	`array_distinct($github.principal.ip_geo_artifact.location.country_or_region)`
`principal_ip_state`	`array_distinct($github.principal.ip_geo_artifact.location.state)`
`principal_ip_city`	`array_distinct($github.principal.location.city)`
`security_result_summary`	`array_distinct($github.security_result.summary)`