O365 FullAccessAsApp Permission Assigned

Description

The following analytic detects the assignment of the 'full_access_as_app' permission to an application registration in Office 365 Exchange Online. This detection leverages Office 365 management activity logs and filters Azure Active Directory workload events to identify when the specific permission, identified by GUID 'dc890d15-9560-4a4c-9b7f-a736ec74ec40', is granted. This activity is significant because it provides extensive control over Office 365 operations, including access to all mailboxes and the ability to send mail as any user. If confirmed malicious, this could lead to unauthorized data access, exfiltration, or account compromise. Immediate investigation is required.

Query · spl

`o365_management_activity` Workload=AzureActiveDirectory Operation="Update application." | eval newvalue = mvindex('ModifiedProperties{}.NewValue',0) | spath input=newvalue | search "{}.ResourceAppId"="00000002-0000-0ff1-ce00-000000000000""{}.RequiredAppPermissions{}.EntitlementId"="dc890d15-9560-4a4c-9b7f-a736ec74ec40" | eval Permissions = '{}.RequiredAppPermissions{}.EntitlementId' | fillnull | stats count min(_time) as firstTime max(_time) as lastTime values(Scope) as Scope by signature dest user src vendor_account vendor_product object user_agent | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_fullaccessasapp_permission_assigned_filter`

Implementation guide

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.

Known false positives

  • The full_access_as_app API permission may be assigned to legitimate applications. Filter as needed.

Analyst notes

Known false positives: The full_access_as_app API permission may be assigned to legitimate applications. Filter as needed.

Raw source O365 FullAccessAsApp Permission Assigned · SPL
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Published by splunk/security_content ↗, licensed under Apache 2.0 ↗. Reproduced here unmodified. 
name: O365 FullAccessAsApp Permission Assigned
id: 01a510b3-a6ac-4d50-8812-7e8a3cde3d79
version: 9
creation_date: '2024-02-14'
modification_date: '2026-05-13'
author: Mauricio Velazco, Splunk
status: production
type: TTP
description: The following analytic detects the assignment of the 'full_access_as_app' permission to an application registration in Office 365 Exchange Online. This detection leverages Office 365 management activity logs and filters Azure Active Directory workload events to identify when the specific permission, identified by GUID 'dc890d15-9560-4a4c-9b7f-a736ec74ec40', is granted. This activity is significant because it provides extensive control over Office 365 operations, including access to all mailboxes and the ability to send mail as any user. If confirmed malicious, this could lead to unauthorized data access, exfiltration, or account compromise. Immediate investigation is required.
data_source:
    - O365 Update application.
search: "`o365_management_activity` Workload=AzureActiveDirectory Operation=\"Update application.\" | eval newvalue = mvindex('ModifiedProperties{}.NewValue',0) | spath input=newvalue | search \"{}.ResourceAppId\"=\"00000002-0000-0ff1-ce00-000000000000\"\"{}.RequiredAppPermissions{}.EntitlementId\"=\"dc890d15-9560-4a4c-9b7f-a736ec74ec40\" | eval Permissions = '{}.RequiredAppPermissions{}.EntitlementId' | fillnull | stats count min(_time) as firstTime max(_time) as lastTime values(Scope) as Scope by signature dest user src vendor_account vendor_product object user_agent | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `o365_fullaccessasapp_permission_assigned_filter`"
how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
known_false_positives: The full_access_as_app API permission may be assigned to legitimate applications. Filter as needed.
references:
    - https://msrc.microsoft.com/blog/2024/01/microsoft-actions-following-attack-by-nation-state-actor-midnight-blizzard/
    - https://www.microsoft.com/en-us/security/blog/2024/01/25/midnight-blizzard-guidance-for-responders-on-nation-state-attack/
    - https://attack.mitre.org/techniques/T1098/002/
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: User $user$ assigned the full_access_as_app permission to the app registration $object$
    entity:
        field: user
        type: user
        score: 50
analytic_story:
    - Office 365 Persistence Mechanisms
    - NOBELIUM Group
asset_type: O365 Tenant
mitre_attack_id:
    - T1098.002
    - T1098.003
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: cloud
security_domain: identity
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1098.002/o365_full_access_as_app_permission_assigned/o365_full_access_as_app_permission_assigned.log
          source: o365:management:activity
          sourcetype: o365:management:activity
      test_type: unit

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