Detection: O365 Add App Role Assignment Grant User

Description

The following analytic detects the addition of an application role assignment grant to a user in Office 365. It leverages data from the o365_management_activity dataset, specifically monitoring the "Add app role assignment grant to user" operation. This activity is significant as it can indicate unauthorized privilege escalation or the assignment of sensitive roles to users. If confirmed malicious, this could allow an attacker to gain elevated permissions, potentially leading to unauthorized access to critical resources and data within the Office 365 environment.

 1`o365_management_activity` Workload=AzureActiveDirectory Operation="Add app role assignment grant to user."
 2  
 3| fillnull
 4  
 5| stats count min(_time) as firstTime max(_time) as lastTime
 6    BY signature dest user
 7       src vendor_account vendor_product
 8  
 9| `security_content_ctime(firstTime)`
10  
11| `security_content_ctime(lastTime)`
12  
13| `o365_add_app_role_assignment_grant_user_filter`

Data Source

Name Platform Sourcetype Source
O365 Add app role assignment grant to user. Other 'o365:management:activity' 'o365'

Macros Used

Name Value
o365_management_activity sourcetype=o365:management:activity
o365_add_app_role_assignment_grant_user_filter search *
o365_add_app_role_assignment_grant_user_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1136.003 Cloud Account Persistence
Installation
DE.CM
CIS 10

Default Configuration

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

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Finding (Notable) Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Intermediate Finding (Risk Event) Yes
TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

Implementation

You must install splunk Microsoft Office 365 add-on. This search works with o365:management:activity

Known False Positives

The creation of a new Federation is not necessarily malicious, however this events need to be followed closely, as it may indicate federated credential abuse or backdoor via federated identities at a different cloud provider.

Associated Analytic Story

Finding

Title Entity Field Entity Type Risk Score
User $user$ added a new app role assignment user user 50

Intermediate Findings

Message Entity Field Entity Type Risk Score
User $user$ added a new app role assignment dest system 50

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation Passing N/A N/A N/A
Unit Passing Dataset o365 o365:management:activity
Integration ✅ Passing Dataset o365 o365:management:activity

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: 12