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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.

  • Type: TTP

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

  • Last Updated: 2024-04-01
  • Author: Steven Dick
  • ID: c6998a30-fef4-4e89-97ac-3bb0123719b4

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1567 Exfiltration Over Web Service Exfiltration
T1114 Email Collection Collection
T1114.002 Remote Email Collection Collection
Kill Chain Phase
  • Actions On Objectives
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`o365_management_activity` Workload=SecurityComplianceCenter Operation=AdminMailAccess 
| 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 
| rename InternetMessageId as signature_id, UserId as src_user 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `o365_email_access_by_security_administrator_filter`

Macros

The SPL above uses the following Macros:

:information_source: o365_email_access_by_security_administrator_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
  • MailboxId
  • InternetMessageId
  • UserId

How To Implement

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

RBA

Risk Score Impact Confidence Message
25.0 50 50 A security administrator $src_user$ accessed email messages for $user$

: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: 1