Suspicious Inbox Forwarding

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.

Sigma rule (View on GitHub)

 1title: Suspicious Inbox Forwarding
 2id: 6c220477-0b5b-4b25-bb90-66183b4089e8
 3status: test
 4description: 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.
 5references:
 6    - https://learn.microsoft.com/en-us/defender-cloud-apps/anomaly-detection-policy
 7    - https://learn.microsoft.com/en-us/defender-cloud-apps/policy-template-reference
 8author: Austin Songer @austinsonger
 9date: 2021/08/22
10modified: 2022/10/09
11tags:
12    - attack.exfiltration
13    - attack.t1020
14logsource:
15    service: threat_management
16    product: m365
17detection:
18    selection:
19        eventSource: SecurityComplianceCenter
20        eventName: 'Suspicious inbox forwarding'
21        status: success
22    condition: selection
23falsepositives:
24    - Unknown
25level: low

References

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