O365 Email Receive and Hard Delete Takeover Behavior
SPLUNK detection rule by Steven Dick · Apache-2.0
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.
name: O365 Email Receive and Hard Delete Takeover Behavior
id: b66aeaa4-586f-428b-8a2b-c4fd3039d8d3
version: 6
creation_date: '2025-01-23'
modification_date: '2026-05-13'
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 ("$user$") | 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: 7d
latest_offset: "0"
- 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: $info_max_time$
intermediate_findings:
entities:
- field: user
type: user
score: 20
message: The user $user$ received and deleted an email within a short timeframe titled [$subject$] which may contain password or banking information
threat_objects:
- field: src
type: ip_address
- field: subject
type: email_subject
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
category: 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
test_type: unit
CIRCL