Detection: O365 Email Password and Payroll Compromise Behavior

Updated Date: 2025-01-20 ID: e36de71a-6bdc-4002-98ff-e3e51b0d8f96 Author: Steven Dick Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies when an O365 email recipient receives and then deletes emails for the combination of both password and 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.

Search

 1`o365_messagetrace` subject IN ("*banking*","*direct deposit*","*pay-to*","*password *","*passcode *","*OTP *","*MFA *","*Account Recovery*")
 2
 3| eval mailtime = _time
 4
 5| bin _time span=4hr
 6
 7| eval user = lower(RecipientAddress)
 8
 9| eval InternetMessageId = lower(MessageId)
10
11| join InternetMessageId, user max=0
12  [
13  
14| search `o365_management_activity` Workload=Exchange Operation IN ("SoftDelete","HardDelete")
15  
16| spath path=AffectedItems{}  output=AffectedItemSplit
17  
18| fields _time,ClientIP,ClientInfoString,UserId,Operation,ResultStatus,MailboxOwnerUPN,AffectedItemSplit 
19  
20| mvexpand AffectedItemSplit 
21| spath input=AffectedItemSplit
22  
23| search Subject IN ("*banking*","*direct deposit*","*pay-to*","*password *","*passcode *","*OTP *","*MFA *","*Account Recovery*") 
24  
25| eval deltime = _time
26  
27| bin _time span=4hr
28  
29| eval InternetMessageId = lower(InternetMessageId), user = lower(UserId)
30  ]
31
32| stats values(ClientInfoString) as http_user_agent, values(ClientIP) as src, values(Subject) as subject, dc(Subject) as subject_count, values(Operation) as action, values(ResultStatus) as result, count, min(mailtime) as firstTime, max(deltime) as lastTime by user,_time
33
34| search subject IN ("*banking*","*direct deposit*","*pay-to*") AND subject IN ("*password *","*passcode *","*OTP *","*MFA *","*Account Recovery*") 
35
36| `security_content_ctime(firstTime)` 
37
38| `security_content_ctime(lastTime)`
39
40| `o365_email_password_and_payroll_compromise_behavior_filter`

Data Source

Name	Platform	Sourcetype	Source
Office 365 Reporting Message Trace	N/A	`'o365:reporting:messagetrace'`	`'o365'`
Office 365 Universal Audit Log	N/A	`'o365:management:activity'`	`'o365'`

Macros Used

Name	Value
o365_management_activity	`sourcetype=o365:management:activity`
o365_email_password_and_payroll_compromise_behavior_filter	`search *`

o365_email_password_and_payroll_compromise_behavior_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
T1070.008	Clear Mailbox Data	Defense Evasion
T1485	Data Destruction	Impact
T1114.001	Local Email Collection	Collection

Actions on Objectives

Exploitation

DE.CM

CIS 10

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 AND Message Trace events.

Known False Positives

Unknown, unlikely.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

The user $user$ received and deleted password and payroll change emails within a short timeframe

Risk Object	Risk Object Type	Risk Score	Threat Objects
user	user	90	src

References

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