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Description

The following analytic identifies the modification of the SourceAnchor (also called ImmutableId) attribute for an Azure Active Directory user. Updating this attribute is a step required to set up the Azure Active Directory identity federation backdoor technique discovered by security researcher Nestori Syynimaa. Similar to Active Directory, Azure AD uses the concept of domains to manage directories of identities. A new Azure AD tenant will initially contain a single domain that is commonly called the cloud-only onmicrosoft.com domain. Organizations can also add their registered custom domains to Azure AD for email addresses to match the organizations domain name. If the organization intends to use a third-party identity provider such as ADFS for authentication, the added custom domains can be configured as federated. An adversary who has obtained privileged access to an Azure AD tenant may leverage this technique to establish persistence and be able to authenticate to Azure AD impersonating any user and bypassing the requirement to have a valid password and/or perform MFA.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2022-09-02
  • Author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk
  • ID: 0c0badad-4536-4a84-a561-5ff760f3c00e

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1098 Account Manipulation Persistence
Kill Chain Phase
  • Installation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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 `azuread` operationName="Update user" properties.targetResources{}.modifiedProperties{}.displayName=SourceAnchor 
| rename properties.* as * 
| rename targetResources{}.userPrincipalName as userPrincipalName 
| rename initiatedBy.user.userPrincipalName as initiatedBy 
| rename callerIpAddress as callerIpAddress 
| rename targetResources{}.modifiedProperties{}.newValue as modifiedProperties 
| stats values(userPrincipalName) as userPrincipalName values(modifiedProperties) by _time, initiatedBy, callerIpAddress, result, operationName 
| `azure_ad_user_immutableid_attribute_updated_filter`

Macros

The SPL above uses the following Macros:

:information_source: azure_ad_user_immutableid_attribute_updated_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time

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. Specifically, this analytic leverages the AuditLogs 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

RBA

Risk Score Impact Confidence Message
45.0 50 90 The SourceAnchor or ImmutableID attribute has been modified for user $userPrincipalName$ by $initiatedBy$

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

Reference

Test Dataset

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

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