Detection: O365 Suspicious Admin Email Forwarding

DEPRECATED DETECTION

This detection has been marked as deprecated by the Splunk Threat Research team. This means that it will no longer be maintained or supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2020-12-16 ID: 7f398cfb-918d-41f4-8db8-2e2474e02c28 Author: Patrick Bareiss, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

DEPRECATION NOTE - This search has been deprecated and replaced with O365 Mailbox Email Forwarding Enabled. This search detects when an admin configured a forwarding rule for multiple mailboxes to the same destination.

1`o365_management_activity` Operation=Set-Mailbox 
2| spath input=Parameters 
3| rename Identity AS src_user 
4| search ForwardingAddress=* 
5| stats dc(src_user) AS count_src_user earliest(_time) as firstTime latest(_time) as lastTime values(src_user) AS src_user values(user) AS user by ForwardingAddress 
6| where count_src_user > 1 
7|`security_content_ctime(firstTime)` 
8|`security_content_ctime(lastTime)` 
9|`o365_suspicious_admin_email_forwarding_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_suspicious_admin_email_forwarding_filter search *
o365_suspicious_admin_email_forwarding_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
T1114.003 Email Forwarding Rule Collection
T1114 Email Collection Collection
KillChainPhase.EXPLOITAITON
NistCategory.DE_AE
Cis18Value.CIS_10
Kimsuky
LAPSUS$
Silent Librarian
Magic Hound
Silent Librarian

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
This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

You must install splunk Microsoft Office 365 add-on. This search works with o365:management:activity

Known False Positives

unknown

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
User $user$ has configured a forwarding rule for multiple mailboxes to the same destination $ForwardingAddress$ 48 80 60
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation Not Applicable 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