Detection: O365 Email Access By Security Administrator

Updated Date: 2024-04-01 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| stats values(Workload) as category, values(MailboxId) as user, values(Operation) as signature, count, min(_time) as firstTime, max(_time) as lastTime by InternetMessageId, UserId 
3| rename InternetMessageId as signature_id, UserId as src_user 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `o365_email_access_by_security_administrator_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
N/A	N/A	N/A	N/A	N/A

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

KillChainPhase.ACTIONS_ON_OBJECTIVES

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

APT28

Magic Hound

Silent Librarian

APT1

APT28

APT29

Chimera

Dragonfly

FIN4

HAFNIUM

Ke3chang

Kimsuky

Leafminer

Magic Hound

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

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

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

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
A security administrator $src_user$ accessed email messages for $user$	25	50	50

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

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: 1