Azure AD User ImmutableId Attribute Updated

name: Azure AD User ImmutableId Attribute Updated
id: 0c0badad-4536-4a84-a561-5ff760f3c00e
version: 11
date: '2026-03-10'
author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk
status: production
type: TTP
description: The following analytic identifies the modification of the SourceAnchor (ImmutableId) attribute for an Azure Active Directory user. This detection leverages Azure AD audit logs, specifically monitoring the "Update user" operation and changes to the SourceAnchor attribute. This activity is significant as it is a step in setting up an Azure AD identity federation backdoor, allowing an adversary to establish persistence. If confirmed malicious, the attacker could impersonate any user, bypassing password and MFA requirements, leading to unauthorized access and potential data breaches.
data_source:
    - Azure Active Directory Update user
search: |-
    `azure_monitor_aad` operationName="Update user" properties.targetResources{}.modifiedProperties{}.displayName=SourceAnchor
      | rename properties.* as *
      | rename initiatedBy.user.userPrincipalName as initiatedBy
      | rename targetResources{}.modifiedProperties{}.newValue as modifiedProperties
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY dest user src
           vendor_account vendor_product initiatedBy
           signature
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `azure_ad_user_immutableid_attribute_updated_filter`
how_to_implement: You must install the latest version of Splunk Add-on for Microsoft Cloud Services from Splunkbase(https://splunkbase.splunk.com/app/3110/#/details). You must be ingesting Azure Active Directory events into your Splunk environment. This analytic was written to be used with the azure:monitor:aad sourcetype leveraging the AuditLog log category.
known_false_positives: The SourceAnchor (also called ImmutableId) Azure AD attribute has legitimate uses for directory synchronization. Investigate and filter as needed.
references:
    - https://docs.microsoft.com/en-us/azure/active-directory/hybrid/plan-connect-design-concepts
    - https://www.mandiant.com/resources/remediation-and-hardening-strategies-microsoft-365-defend-against-apt29-v13
    - https://o365blog.com/post/federation-vulnerability/
    - https://www.inversecos.com/2021/11/how-to-detect-azure-active-directory.html
    - https://www.mandiant.com/resources/blog/detecting-microsoft-365-azure-active-directory-backdoors
    - https://attack.mitre.org/techniques/T1098/
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search  user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: The SourceAnchor or ImmutableID attribute has been modified for user $user$ by $initiatedBy$
    risk_objects:
        - field: user
          type: user
          score: 50
        - field: initiatedBy
          type: user
          score: 50
    threat_objects: []
tags:
    analytic_story:
        - Azure Active Directory Persistence
        - Hellcat Ransomware
    asset_type: Azure Active Directory
    mitre_attack_id:
        - T1098
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1098/azure_ad_set_immutableid/azure-audit.log
          source: Azure AD
          sourcetype: azure:monitor:aad