ID | Technique | Tactic |
---|---|---|
T1114 | Email Collection | Collection |
Detection: O365 New Forwarding Mailflow Rule Created
Description
The following analytic detects the creation of new mail flow rules in Office 365 that may redirect or copy emails to unauthorized or external addresses. It leverages Office 365 Management Activity logs, specifically querying for the "New-TransportRule" operation and parameters like "BlindCopyTo", "CopyTo", and "RedirectMessageTo". This activity is significant as it can indicate potential data exfiltration or unauthorized access to sensitive information. If confirmed malicious, attackers could intercept or redirect email communications, leading to data breaches or information leakage.
Search
1`o365_management_activity` Workload=Exchange Operation="New-TransportRule"
2| eval match1=mvfind('Parameters{}.Name', "BlindCopyTo")
3| eval match2=mvfind('Parameters{}.Name', "CopyTo")
4| eval match3=mvfind('Parameters{}.Name', "RedirectMessageTo")
5| where match1>= 0 OR match2>= 0 OR match3>=0
6| eval ForwardTo=coalesce(BlindCopyTo, CopyTo, RedirectMessageTo)
7| search ForwardTo!=""
8| rename UserId as user
9| stats count earliest(_time) as firstTime latest(_time) as lastTime by Operation, user, Name, ForwardTo
10| `security_content_ctime(firstTime)`
11| `security_content_ctime(lastTime)`
12| `o365_new_forwarding_mailflow_rule_created_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
N/A | N/A | N/A | N/A | N/A |
Macros Used
Name | Value |
---|---|
o365_management_activity | sourcetype=o365:management:activity |
o365_new_forwarding_mailflow_rule_created_filter | search * |
o365_new_forwarding_mailflow_rule_created_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 Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.
Known False Positives
Forwarding mail flow rules may be created for legitimate reasons, filter as needed.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
A new forwarding mailflow rule was created by $user$ | 42 | 70 | 60 |
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: 2