github_high_number_of_non_public_github_repositories_downloaded

rule github_high_number_of_non_public_github_repositories_downloaded {

  meta:
    author = "Google Cloud Security"
    description = "Detects when a user downloads a high number of non-public GitHub repositories. An adversary may attempt to steal the contents of several GitHub repositories after compromising a user account."
    rule_id = "mr_549561b8-1088-4a08-b1f4-a1029a142919"
    rule_name = "GitHub High Number Of Non Public GitHub Repositories Downloaded"
    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"
    mitre_attack_tactic = "Collection"
    mitre_attack_technique = "Data from Information Repositories: Code Repositories"
    mitre_attack_url = "https://attack.mitre.org/versions/v14/techniques/T1213/003/"
    mitre_attack_version = "v14"
    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.download_zip"
    $github.extracted.fields["public_repo"] = "false"
    $github.principal.user.userid = $user_id
    $github.target.resource.name = $github_repo_name

  match:
    $user_id over 30m

  outcome:
    $github_repo_name_distinct_count = count_distinct($github_repo_name)
    $risk_score = max(85)
    $mitre_attack_tactic = "Collection"
    $mitre_attack_technique = "Data from Information Repositories: Code Repositories"
    $mitre_attack_technique_id = "T1213.003"
    $event_count = count_distinct($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:
    // Customize GitHub repo count to fit your environment
    $github and $github_repo_name_distinct_count > 5
}