Detection: O365 Admin Consent Bypassed by Service Principal

Description

The following analytic identifies instances where a service principal in Office 365 Azure Active Directory assigns app roles without standard admin consent. It leverages o365_management_activity logs, specifically focusing on the 'Add app role assignment to service principal' operation. This activity is significant for SOCs as it may indicate a bypass of critical administrative controls, potentially leading to unauthorized access or privilege escalation. If confirmed malicious, this could allow an attacker to misuse automated processes to assign sensitive permissions, compromising the security of the environment.

Search

 1`o365_management_activity` Workload=AzureActiveDirectory Operation="Add app role assignment to service principal." 
 2| eval len=mvcount('Actor{}.ID') 
 3| eval userType = mvindex('Actor{}.ID',len-1) 
 4| eval roleId = mvindex('ModifiedProperties{}.NewValue', 0) 
 5| eval roleValue = mvindex('ModifiedProperties{}.NewValue', 1) 
 6| eval roleDescription = mvindex('ModifiedProperties{}.NewValue', 2) 
 7| eval dest_user = mvindex('Target{}.ID', 0) 
 8| search userType = "ServicePrincipal" 
 9| eval src_user = user 
10| fillnull 
11| stats count min(_time) as firstTime max(_time) as lastTime by signature dest user src vendor_account vendor_product dest_user roleId roleValue roleDescription 
12| `security_content_ctime(firstTime)` 
13| `security_content_ctime(lastTime)` 
14| `o365_admin_consent_bypassed_by_service_principal_filter`

Data Source

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 Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.

Known False Positives

Service Principals are sometimes configured to legitimately bypass the consent process for purposes of automation. Filter as needed.

Associated Analytic Story

• Office 365 Persistence Mechanisms

Finding

References

• https://winsmarts.com/how-to-grant-admin-consent-to-an-api-programmatically-e32f4a100e9d

• 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/T1098/003/

• https://msrc.microsoft.com/blog/2024/01/microsoft-actions-following-attack-by-nation-state-actor-midnight-blizzard/

• 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: 9