Azure AD New Custom Domain Added

SPLUNK detection rule by Mauricio Velazco, Gowthamaraj Rajendran, Splunk · Apache-2.0

The following analytic detects the addition of a new custom domain within an Azure Active Directory (AD) tenant. It leverages Azure AD AuditLogs to identify successful "Add unverified domain" operations. This activity is significant as it may indicate an adversary attempting to establish persistence by setting up identity federation backdoors, allowing them to impersonate users and bypass authentication mechanisms. If confirmed malicious, this could enable attackers to gain unauthorized access, escalate privileges, and maintain long-term access to the Azure AD environment, posing a severe security risk.

name: Azure AD New Custom Domain Added
id: 30c47f45-dd6a-4720-9963-0bca6c8686ef
version: 13
creation_date: '2022-09-02'
modification_date: '2026-05-13'
author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk
status: production
type: TTP
description: The following analytic detects the addition of a new custom domain within an Azure Active Directory (AD) tenant. It leverages Azure AD AuditLogs to identify successful "Add unverified domain" operations. This activity is significant as it may indicate an adversary attempting to establish persistence by setting up identity federation backdoors, allowing them to impersonate users and bypass authentication mechanisms. If confirmed malicious, this could enable attackers to gain unauthorized access, escalate privileges, and maintain long-term access to the Azure AD environment, posing a severe security risk.
data_source:
    - Azure Active Directory Add unverified domain
search: |-
    `azure_monitor_aad` operationName="Add unverified domain" properties.result=success
      | rename properties.* as *
      | rename targetResources{}.displayName as domain
      | rename userAgent as user_agent
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY dest user src
           vendor_account vendor_product user_agent
           domain signature
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `azure_ad_new_custom_domain_added_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 AuditLogs log category.
known_false_positives: In most organizations, new customm domains will be updated infrequently. Filter as needed.
references:
    - https://docs.microsoft.com/en-us/azure/active-directory/enterprise-users/domains-manage
    - 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/T1484/002/
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 ("$user$") | 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: 7d
      latest_offset: "0"
finding:
    title: A new custom domain, $domain$ , was added by $user$
    entity:
        field: user
        type: user
        score: 50
analytic_story:
    - Azure Active Directory Persistence
asset_type: Azure Active Directory
mitre_attack_id:
    - T1484.002
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1484.002/new_federated_domain/azure-audit.log
          source: Azure AD
          sourcetype: azure:monitor:aad
      test_type: unit

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

f94e3a55-93dc-47f1-a2c8-cf8a00113c6d

Propose edits, view related rules, and engage with the community through comments.

Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

[[ reason ]]

What does this mean?

Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

Community Discussion