ID | Technique | Tactic |
---|---|---|
T1098 | Account Manipulation | Persistence |
Detection: Azure AD User ImmutableId Attribute Updated
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
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 |
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
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 |
References
-
https://docs.microsoft.com/en-us/azure/active-directory/hybrid/plan-connect-design-concepts
-
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
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