Detection: Azure AD User ImmutableId Attribute Updated

Updated Date: 2024-09-30 ID: 0c0badad-4536-4a84-a561-5ff760f3c00e Author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk Type: TTP Product: Splunk Enterprise Security

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.

Search

1`azure_monitor_aad`  operationName="Update user" properties.targetResources{}.modifiedProperties{}.displayName=SourceAnchor 
2| rename properties.* as * 
3| rename initiatedBy.user.userPrincipalName as initiatedBy 
4| rename targetResources{}.modifiedProperties{}.newValue as modifiedProperties 
5| stats count min(_time) as firstTime max(_time) as lastTime values(user) as user values(modifiedProperties) as modifiedProperties by initiatedBy, src_ip, result, operationName 
6| `security_content_ctime(firstTime)` 
7| `security_content_ctime(lastTime)` 
8| `azure_ad_user_immutableid_attribute_updated_filter`

Data Source

Name	Platform	Sourcetype	Source
Azure Active Directory Update user	Azure	`'azure:monitor:aad'`	`'Azure AD'`

Macros Used

Name	Value
azure_monitor_aad	`sourcetype=azure:monitor:aad`
azure_ad_user_immutableid_attribute_updated_filter	`search *`

azure_ad_user_immutableid_attribute_updated_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
T1098	Account Manipulation	Persistence

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

HAFNIUM

Lazarus Group

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 Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

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.

Associated Analytic Story

Azure Active Directory Persistence

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
The SourceAnchor or ImmutableID attribute has been modified for user $user$ by $initiatedBy$	45	50	90

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`Azure AD`	`azure:monitor:aad`
Integration	✅ Passing	Dataset	`Azure AD`	`azure:monitor:aad`

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: 4