ID | Technique | Tactic |
---|---|---|
T1114.002 | Remote Email Collection | Collection |
T1114 | Email Collection | Collection |
T1098 | Account Manipulation | Persistence |
T1098.003 | Additional Cloud Roles | Privilege Escalation |
Detection: O365 Mailbox Read Access Granted to Application
Description
The following analytic identifies instances where the Mail.Read Graph API permissions are granted to an application registration within an Office 365 tenant. It leverages O365 audit logs, specifically events related to changes in application permissions within the AzureActiveDirectory workload. This activity is significant because the Mail.Read permission allows applications to access and read all emails within a user's mailbox, which often contain sensitive or confidential information. If confirmed malicious, this could lead to data exfiltration, spear-phishing attacks, or further compromise based on the information gathered from the emails.
Search
1`o365_management_activity` Operation="Update application."
2| eval json_data=mvindex('ModifiedProperties{}.NewValue', 0)
3| eval json_data=replace(json_data, "^\[\s*", "")
4| eval json_data=replace(json_data, "\s*\]$", "")
5| spath input=json_data path=RequiredAppPermissions{}.EntitlementId output=EntitlementIds
6| eval match_found=mvfind(EntitlementIds, "810c84a8-4a9e-49e6-bf7d-12d183f40d01")
7| where isnotnull(match_found)
8| stats max(_time) as lastTime values(EntitlementIds) as EntitlementIds by Operation, user, object
9| `security_content_ctime(lastTime)`
10| `o365_mailbox_read_access_granted_to_application_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
O365 Update application. | N/A | 'o365:management:activity' |
'o365' |
N/A |
Macros Used
Name | Value |
---|---|
o365_management_activity | sourcetype=o365:management:activity |
o365_mailbox_read_access_granted_to_application_filter | search * |
o365_mailbox_read_access_granted_to_application_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
Known False Positives
There are legitimate scenarios in wich an Application registrations requires Mailbox read access. Filter as needed.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
Application registration $object$ was grandes mailbox read access by $user$ | 45 | 90 | 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: 2