Try in Splunk Security Cloud

Description

This detection is crafted to monitor and identify the creation of new email forwarding rules in an Office 365 environment. It specifically targets events logged under New-InboxRule and Set-InboxRule operations within o365_management_activity, indicating the establishment or modification of inbox rules that forward emails. The detection checks for the presence of parameters such as ForwardTo, ForwardAsAttachmentTo, and RedirectTo, which are key indicators of email forwarding behavior.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-03-27
  • Author: Mauricio Velazco, Splunk
  • ID: 68469fd0-1315-44ba-b7e4-e92847bb76d6

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1114 Email Collection Collection
T1114.003 Email Forwarding Rule Collection
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


1
2
3
4
5
6
7
8
9
10



`o365_management_activity` (Operation=New-InboxRule OR Operation=set-InboxRule) 
| eval match1=mvfind('Parameters{}.Name', "ForwardTo") 
| eval match2=mvfind('Parameters{}.Name', "ForwardAsAttachmentTo") 
| eval match3=mvfind('Parameters{}.Name', "RedirectTo") 
| where match1>= 0 OR match2>= 0 OR match3>= 0 
| eval ForwardTo=coalesce(ForwardTo, ForwardAsAttachmentTo, RedirectTo) 
| stats count min(_time) as firstTime max(_time) as lastTime values(Name) as Name by user Operation ForwardTo 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `o365_new_email_forwarding_rule_created_filter`

Macros

The SPL above uses the following Macros:

:information_source: o365_new_email_forwarding_rule_created_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Operation
  • Parameters{}.Name
  • Name
  • user
  • UserId

How To Implement

You must install the Splunk Microsoft Office 365 Add-on and ingest Office 365 management activity events.

Known False Positives

Users may create email forwarding rules for legitimate purposes. Filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
42.0 70 60 A forwarding email inbox rule was created for $user$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 1