Microsoft 365 Exchange DKIM Signing Configuration Disabled

Identifies when a DomainKeys Identified Mail (DKIM) signing configuration is disabled in Microsoft 365. With DKIM in Microsoft 365, messages that are sent from Exchange Online will be cryptographically signed. This will allow the receiving email system to validate that the messages were generated by a server that the organization authorized and were not spoofed.

Rule type: query

Rule indices:

filebeat-*
logs-o365*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-30m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://docs.microsoft.com/en-us/powershell/module/exchange/set-dkimsigningconfig?view=exchange-ps

Tags:

Elastic
Cloud
Microsoft 365
Continuous Monitoring
SecOps
Data Protection
Persistence

Version: 9

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Setup

The Office 365 Logs Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.

Rule query

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event.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:"Set-DkimSigningConfig" and o365.audit.Parameters.Enabled:False and event.outcome:success

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Modify Authentication Process
- ID: T1556
- Reference URL: https://attack.mitre.org/techniques/T1556/

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