O365 OneDrive Anonymous Link Created or Updated

// Copyright 2025 Google LLC. Licensed under Apache-2.0.

rule o365_onedrive_anonymous_link_created_updated {

  meta:
    author = "Google Cloud Security"
    description = "Anonymous links can be used to export files from OneDrive. While this isn't always a sign of malicious activity, some organizations do not support the creation of anonymous links because of the risk of data leakage. This rule detects the creation or modification of anonymous links in OneDrive."
    rule_id = "mr_3e2572c1-cc14-4c2b-b60b-434db1b0f4ae"
    rule_name = "O365 OneDrive Anonymous Link Created or Updated"
    type = "hunt"
    platform = "azure"
    data_source = "o365"
    severity = "Medium"
    priority = "Medium"

  events:
    (
        (
            $file.metadata.event_type = "USER_RESOURCE_CREATION" and
            $file.metadata.product_event_type = "AnonymousLinkCreated"
        )
    or
        (
            $file.metadata.event_type = "STATUS_UPDATE" and
            $file.metadata.product_event_type = "AnonymousLinkUpdated"
        )
    )
    $file.metadata.product_name = "Office 365"
    $file.metadata.vendor_name = "Microsoft"
    $file.principal.user.userid = $user

  match:
    $user over 5m

  outcome:
    $risk_score = 35
    $event_count = count_distinct($file.metadata.id)
    $referral_url = array_distinct($file.network.http.referral_url)
    $user_agent = array_distinct($file.network.http.user_agent)
    $principal_application = array_distinct($file.principal.application)
    //The IP address for creation is a Microsoft IP address while update is the system making the change
    $principal_ip = array_distinct($file.principal.ip)
    $target_application = array_distinct($file.target.application)
    $principal_user_userid = array_distinct($file.principal.user.userid)
    $target_file_full_path = array_distinct($file.target.file.full_path)
    $target_url = array_distinct($file.target.url)

  condition:
    $file
}