Suspicious Inbox Forwarding — Sigma Rule

Rule metadata and linked tags

Author: Austin Songer @austinsonger. Source status: test; severity: low. Source dates: 2021-08-22 / 2022-10-09.

{
  "service": "threat_management",
  "product": "m365"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 896c0db274f2702806403d8688f3d8da72f7e4aab3f8b853cc8c5a991a14a655

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Suspicious Inbox Forwarding
id: 6c220477-0b5b-4b25-bb90-66183b4089e8
status: test
description: Detects when a Microsoft Cloud App Security reported suspicious email forwarding rules, for example, if a user created an inbox rule that forwards a copy of all emails to an external address.
references:
    - https://learn.microsoft.com/en-us/defender-cloud-apps/anomaly-detection-policy
    - https://learn.microsoft.com/en-us/defender-cloud-apps/policy-template-reference
author: Austin Songer @austinsonger
date: 2021-08-22
modified: 2022-10-09
tags:
    - attack.exfiltration
    - attack.t1020
logsource:
    service: threat_management
    product: m365
detection:
    selection:
        eventSource: SecurityComplianceCenter
        eventName: 'Suspicious inbox forwarding'
        status: success
    condition: selection
falsepositives:
    - Unknown
level: low

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://learn.microsoft.com/en-us/defender-cloud-apps/anomaly-detection-policy
• https://learn.microsoft.com/en-us/defender-cloud-apps/policy-template-reference