ID | Technique | Tactic |
---|---|---|
T1070.008 | Clear Mailbox Data | Defense Evasion |
T1485 | Data Destruction | Impact |
T1114.001 | Local Email Collection | Collection |
Detection: O365 Email Receive and Hard Delete Takeover Behavior
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.
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 ("HardDelete") AND Folder.Path IN ("\\Sent Items","\\Recoverable Items\\Deletions")
15
16| spath path=AffectedItems{} output=AffectedItemSplit
17
18| fields _time,ClientProcessName,ClientIPAddress,ClientInfoString,UserId,Operation,ResultStatus,MailboxOwnerUPN,AffectedItemSplit,Folder.Path
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), subject = Subject
30 ]
31
32| 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
33
34| `security_content_ctime(firstTime)`
35
36| `security_content_ctime(lastTime)`
37
38| `o365_email_receive_and_hard_delete_takeover_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_receive_and_hard_delete_takeover_behavior_filter | search * |
o365_email_receive_and_hard_delete_takeover_behavior_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 Risk Event | True |
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
Possible new user/account onboarding processes.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message:
The user $user$ received and deleted an email within a short timeframe titled [$subject$] which may contain password or banking information
Risk Object | Risk Object Type | Risk Score | Threat Objects |
---|---|---|---|
user | user | 80 | subject, 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