O365 SharePoint Allowed Domains Policy Changed

name: O365 SharePoint Allowed Domains Policy Changed
id: b0cc6fa8-39b1-49ac-a4fe-f2f2a668e06c
version: 11
creation_date: '2024-04-07'
modification_date: '2026-05-13'
author: Steven Dick
status: production
type: TTP
description: The following analytic identifies when the allowed domain settings for O365 SharePoint have been changed. With Azure AD B2B collaboration, users and administrators can invite external users to collaborate with internal users. External guest account invitations may also need access to OneDrive/SharePoint resources. These changed should be monitored by security teams as they could potentially lead to unauthorized access.
data_source:
    - Office 365 Universal Audit Log
search: '`o365_management_activity` Workload=SharePoint Operation=SharingPolicyChanged "ModifiedProperties{}.Name"=AllowDomainList | eval signature_id = CorrelationId, signature=Operation, src = ClientIP, user = UserId, object_name=''ModifiedProperties{}.Name'', object_attrs_new = split(replace(''ModifiedProperties{}.NewValue'',"\.\.\.",""),","), object_attrs_old = split(replace(''ModifiedProperties{}.OldValue'',"\.\.\.",""),",") | fillnull | stats values(object_attrs_new) as object_attrs_new, values(object_attrs_old) as object_attrs_old, values(src) as src, count, min(_time) as firstTime, max(_time) as lastTime by user,signature,signature_id,object_name,dest,action,vendor_account,vendor_product | eval diff_add=mvmap(object_attrs_new,if(isnull(mvfind(object_attrs_old,object_attrs_new)),object_attrs_new,null)) | eval diff_remove=mvmap(object_attrs_old,if(isnull(mvfind(object_attrs_new,object_attrs_old)),object_attrs_old,null)) | eval result = case(isnotnull(diff_add),"Added ".mvjoin(diff_add,","),isnotnull(diff_remove),"Removed ".mvjoin(diff_remove,",")), action = case(isnotnull(diff_add),"created",isnotnull(diff_remove),"deleted") | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_sharepoint_allowed_domains_policy_changed_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://learn.microsoft.com/en-us/sharepoint/external-sharing-overview
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: The SharePoint Online domain allowlist was changed by $user$, $result$
    entity:
        field: user
        type: user
        score: 50
analytic_story:
    - Azure Active Directory Persistence
asset_type: O365 Tenant
mitre_attack_id:
    - T1136.003
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/T1566/o365_various_alerts/o365_various_alerts.log
          sourcetype: o365:management:activity
          source: o365
      test_type: unit