O365 Email Receive and Hard Delete Takeover Behavior

name: O365 Email Receive and Hard Delete Takeover Behavior
id: b66aeaa4-586f-428b-8a2b-c4fd3039d8d3
version: 4
date: '2026-03-10'
author: Steven Dick
status: production
type: Anomaly
description: The following analytic identifies when an O365 email recipient receives and then deletes emails related to password or banking/payroll changes within a short period. This behavior may indicate a compromised account where the threat actor is attempting to redirect the victims payroll to an attacker controlled bank account.
data_source:
    - Office 365 Universal Audit Log
    - Office 365 Reporting Message Trace
search: |-
    `o365_messagetrace` subject IN ("*banking*","*direct deposit*","*pay-to*","*password *","*passcode *","*OTP *","*MFA *","*Account Recovery*")
    | eval mailtime = _time
    | bin _time span=4hr
    | eval user = lower(RecipientAddress)
    | eval InternetMessageId = lower(MessageId)
    | join InternetMessageId, user max=0
      [
      | search `o365_management_activity` Workload=Exchange Operation IN ("HardDelete") AND Folder.Path IN ("\\Sent Items","\\Recoverable Items\\Deletions")
      | spath path=AffectedItems{}  output=AffectedItemSplit
      | fields _time,ClientProcessName,ClientIPAddress,ClientInfoString,UserId,Operation,ResultStatus,MailboxOwnerUPN,AffectedItemSplit,Folder.Path
      | mvexpand AffectedItemSplit | spath input=AffectedItemSplit
      | search Subject IN ("*banking*","*direct deposit*","*pay-to*","*password *","*passcode *","*OTP *","*MFA *","*Account Recovery*")
      | eval deltime = _time
      | bin _time span=4hr
      | eval InternetMessageId = lower(InternetMessageId), user = lower(UserId), subject = Subject
      ]
    | stats values(ClientIPAddress) as src, values(ClientInfoString) as http_user_agent, values(Folder.Path) as file_path, values(Operation) as signature, values(ResultStatus) as result, values(InternetMessageId) as signature_id, count, min(mailtime) as firstTime, max(deltime) as lastTime by user,subject
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `o365_email_receive_and_hard_delete_takeover_behavior_filter`
how_to_implement: You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events AND Message Trace events.
known_false_positives: Possible new user/account onboarding processes.
references:
    - https://attack.mitre.org/techniques/T1114/
    - https://www.hhs.gov/sites/default/files/help-desk-social-engineering-sector-alert-tlpclear.pdf
    - https://intelligence.abnormalsecurity.com/attack-library/threat-actor-convincingly-impersonates-employee-requesting-direct-deposit-update-in-likely-ai-generated-attack
drilldown_searches:
    - name: View the detection results for - "$user$"
      search: '%original_detection_search% | search user = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$user$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$user$") 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: $info_max_time$
    - name: Investigate Email for $user$
      search: '`o365_messagetrace` subject IN ("*banking*","*direct deposit*","*pay-to*","*password *","*passcode *","*OTP *","*MFA *","*Account Recovery*") AND RecipientAddress = "$user$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
rba:
    message: The user $user$ received and deleted an email within a short timeframe titled [$subject$] which may contain password or banking information
    risk_objects:
        - field: user
          type: user
          score: 20
    threat_objects:
        - field: subject
          type: email_subject
        - field: src
          type: ip_address
tags:
    analytic_story:
        - Office 365 Account Takeover
        - Office 365 Collection Techniques
        - Suspicious Emails
        - Data Destruction
    asset_type: O365 Tenant
    mitre_attack_id:
        - T1070.008
        - T1485
        - T1114.001
    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/T1114/o365_suspect_email_actions/o365_exchange_suspect_events.log
          source: o365
          sourcetype: o365:management:activity
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1114/o365_suspect_email_actions/o365_messagetrace_suspect_events.log
          source: o365_messagetrace
          sourcetype: o365:reporting:messagetrace