Detection: O365 Email Access By Security Administrator

Updated Date: 2026-05-13 ID: c6998a30-fef4-4e89-97ac-3bb0123719b4 Author: Steven Dick Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies when a user with sufficient access to O365 Security & Compliance portal uses premium investigation features (Threat Explorer) to directly view email. Adversaries may exploit privileged access with this premium feature to enumerate or exfiltrate sensitive data.

Search

 1`o365_management_activity` Workload=SecurityComplianceCenter Operation=AdminMailAccess
 2  
 3| rename InternetMessageId as signature_id, UserId as src_user
 4  
 5| fillnull
 6  
 7| stats count min(_time) as firstTime max(_time) as lastTime
 8    BY signature dest user
 9       src vendor_account vendor_product
10       src_user signature_id
11  
12| `security_content_ctime(firstTime)`
13  
14| `security_content_ctime(lastTime)`
15  
16| `o365_email_access_by_security_administrator_filter`

Data Source

Name	Platform	Sourcetype	Source
Office 365 Universal Audit Log	Other	`'o365:management:activity'`	`'o365'`

Macros Used

Name	Value
o365_management_activity	`sourcetype=o365:management:activity`
o365_email_access_by_security_administrator_filter	`search *`

o365_email_access_by_security_administrator_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
T1114.002	Remote Email Collection	Collection
T1567	Exfiltration Over Web Service	Exfiltration

Actions on Objectives

Exploitation

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 the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events. Threat Explorer is a premium feature with o365, logging may not be available with proper license.

Known False Positives

Legitamate access by security administators for incident response measures.

Associated Analytic Story

Finding

Title	Entity Field	Entity Type	Risk Score
A security administrator $src_user$ accessed email messages for $user$	src_user	user	50

Intermediate Findings

Message	Entity Field	Entity Type	Risk Score
A security administrator $src_user$ accessed email messages for $user$	user	user	50

References

https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/threat-explorer-investigate-delivered-malicious-email?view=o365-worldwide

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: 11