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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.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-11
  • Author: Mauricio Velazco, Splunk
  • ID: 01a510b3-a6ac-4d50-8812-7e8a3cde3d79

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1098.002 Additional Email Delegate Permissions Persistence, Privilege Escalation
T1098.003 Additional Cloud Roles Persistence, Privilege Escalation
Kill Chain Phase
  • Installation
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`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' 
| stats count earliest(_time) as firstTime latest(_time) as lastTime values(Permissions) by user, object, user_agent, Operation 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `o365_fullaccessasapp_permission_assigned_filter`

Macros

The SPL above uses the following Macros:

:information_source: o365_fullaccessasapp_permission_assigned_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Workload
  • Operation
  • ModifiedProperties{}.NewValue
  • object
  • user
  • user_agent

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.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
48.0 80 60 User $user$ assigned the full_access_as_app permission to the app registration $object$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 2