Detection: Azure AD FullAccessAsApp Permission Assigned

Description

The following analytic detects the assignment of the 'full_access_as_app' permission to an application within Office 365 Exchange Online. This is identified by the GUID 'dc890d15-9560-4a4c-9b7f-a736ec74ec40' and the ResourceAppId '00000002-0000-0ff1-ce00-000000000000'. The detection leverages the azure_monitor_aad data source, focusing on AuditLogs with the operation name 'Update application'. This activity is significant as it grants broad control over Office 365 operations, including full access to all mailboxes and the ability to send emails as any user. If malicious, this could lead to unauthorized access and data exfiltration.

Search

1`azure_monitor_aad` category=AuditLogs operationName="Update application"  
2| eval newvalue = mvindex('properties.targetResources{}.modifiedProperties{}.newValue',0) 
3| spath input=newvalue  
4| search "{}.ResourceAppId"="00000002-0000-0ff1-ce00-000000000000"  "{}.RequiredAppPermissions{}.EntitlementId"="dc890d15-9560-4a4c-9b7f-a736ec74ec40" 
5| eval Permissions = '{}.RequiredAppPermissions{}.EntitlementId' 
6| stats count earliest(_time) as firstTime latest(_time) as lastTime values(Permissions) by user, object, user_agent, operationName 
7| `security_content_ctime(firstTime)` 
8| `security_content_ctime(lastTime)` 
9| `azure_ad_fullaccessasapp_permission_assigned_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Azure Active Directory Update application	Azure	'azure:monitor:aad'	'Azure AD'	N/A

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

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 through an EventHub. This analytic was written to be used with the azure:monitor:aad sourcetype leveraging the AuditLogs log category.

Known False Positives

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

Associated Analytic Story

• Azure Active Directory Persistence

• NOBELIUM Group

Risk Based Analytics (RBA)

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/

Detection Testing

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

Source: GitHub | Version: 2