Microsoft 365 Exchange Transport Rule Modification

Elastic Stack Serverless Security

Identifies when a transport rule has been disabled or deleted in Microsoft 365. Mail flow rules (also known as transport rules) are used to identify and take action on messages that flow through your organization. An adversary or insider threat may modify a transport rule to exfiltrate data or evade defenses.

Rule type: query

Rule indices:

• filebeat-*
• logs-o365*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-30m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://docs.microsoft.com/en-us/powershell/module/exchange/remove-transportrule?view=exchange-ps
• https://docs.microsoft.com/en-us/powershell/module/exchange/disable-transportrule?view=exchange-ps
• https://docs.microsoft.com/en-us/exchange/security-and-compliance/mail-flow-rules/mail-flow-rules

Tags:

• Elastic
• Cloud
• Microsoft 365
• Continuous Monitoring
• SecOps
• Configuration Audit

Version: 5

Rule authors:

• Elastic

Rule license: Elastic License v2

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

event.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:("Remove-TransportRule" or "Disable-TransportRule") and event.outcome:success

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Exfiltration
  • ID: TA0010
  • Reference URL: https://attack.mitre.org/tactics/TA0010/

• Technique:

  • Name: Transfer Data to Cloud Account
  • ID: T1537
  • Reference URL: https://attack.mitre.org/techniques/T1537/