O365 Cross-Tenant Access Change

name: O365 Cross-Tenant Access Change
id: 7c0fa490-12b0-4d0b-b9f5-e101d1e0e06f
version: 7
date: '2026-03-10'
author: Steven Dick
status: production
type: TTP
description: The following analytic identifies when cross-tenant access/synchronization policies are changed in an Azure tenant. Adversaries have been observed altering victim cross-tenant policies as a method of lateral movement or maintaining persistent access to compromised environments. These policies should be considered sensitive and monitored for changes and/or loose configuration.
data_source:
    - Office 365 Universal Audit Log
search: "`o365_management_activity` Workload=AzureActiveDirectory Operation IN (\"Add a partner to cross-tenant access setting.\",\"Delete partner specific cross-tenant access setting.\") | eval user = case(match(mvindex('Actor{}.ID',-1),\"User\"),mvindex('Actor{}.ID',0),match(mvindex('Actor{}.ID',-1),\"ServicePrincipal\"),mvindex('Actor{}.ID',3),true(),mvindex('Actor{}.ID',0)) | fillnull | stats count min(_time) as firstTime max(_time) as lastTime by dest user src vendor_account vendor_product signature signature_id | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_cross_tenant_access_change_filter`"
how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
known_false_positives: Business approved changes by known administrators.
references:
    - https://attack.mitre.org/techniques/T1484/002/
    - https://thehackernews.com/2023/08/emerging-attacker-exploit-microsoft.html
    - https://cyberaffairs.com/news/emerging-attacker-exploit-microsoft-cross-tenant-synchronization/
    - https://www.crowdstrike.com/blog/crowdstrike-defends-against-azure-cross-tenant-synchronization-attacks/
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 user [$user$] changed the Azure cross-tenant access settings
    risk_objects:
        - field: user
          type: user
          score: 50
    threat_objects: []
tags:
    analytic_story:
        - Azure Active Directory Persistence
    asset_type: O365 Tenant
    mitre_attack_id:
        - T1484.002
    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/o365_azure_workload_events/o365_azure_workload_events.log
          sourcetype: o365:management:activity
          source: o365