O365 Email Access By Security Administrator

name: O365 Email Access By Security Administrator
id: c6998a30-fef4-4e89-97ac-3bb0123719b4
version: 9
date: '2026-03-10'
author: Steven Dick
status: production
type: TTP
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.
data_source:
    - Office 365 Universal Audit Log
search: |-
    `o365_management_activity` Workload=SecurityComplianceCenter Operation=AdminMailAccess
      | rename InternetMessageId as signature_id, UserId as src_user
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY signature dest user
           src vendor_account vendor_product
           src_user signature_id
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `o365_email_access_by_security_administrator_filter`
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.
references:
    - https://learn.microsoft.com/en-us/microsoft-365/security/office-365-security/threat-explorer-investigate-delivered-malicious-email?view=o365-worldwide
drilldown_searches:
    - name: View the detection results for - "$user$" and "$src_user$"
      search: '%original_detection_search% | search  user = "$user$" src_user = "$src_user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$" and "$src_user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$", "$src_user$") starthoursago=168  | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: A security administrator $src_user$ accessed email messages for $user$
    risk_objects:
        - field: user
          type: user
          score: 50
        - field: src_user
          type: user
          score: 50
    threat_objects: []
tags:
    analytic_story:
        - Data Exfiltration
        - Azure Active Directory Account Takeover
        - Office 365 Account Takeover
    asset_type: O365 Tenant
    mitre_attack_id:
        - T1114.002
        - T1567
    product:
        - Splunk Enterprise
        - Splunk Enterprise Security
        - Splunk Cloud
    security_domain: threat
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1566/o365_various_alerts/o365_various_alerts.log
          sourcetype: o365:management:activity
          source: o365