Microsoft 365 Exchange Transport Rule Creation

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Microsoft 365 Exchange Transport Rule Creation

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Identifies a transport rule creation in Microsoft 365. As a best practice, Exchange Online mail transport rules should not be set to forward email to domains outside of your organization. An adversary may create transport rules to exfiltrate data.

Rule type: query

Rule indices:

  • filebeat-*
  • logs-o365*

Severity: medium

Risk score: 47

Runs every: 5 minutes

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

Maximum alerts per execution: 100

References:

Tags:

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

Version: 101 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 8.6.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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A new transport rule may be created by a system or network administrator. Verify that the configuration change was expected. Exceptions can be added to this rule to filter expected behavior.

Investigation guide

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Rule query

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event.dataset:o365.audit and event.provider:Exchange and
event.category:web and event.action:"New-TransportRule" and
event.outcome:success

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 101 (8.6.0 release)
  • Formatting only
Version 100 (8.5.0 release)
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Version 8 (8.4.0 release)
  • Formatting only
Version 6 (8.2.0 release)
  • Formatting only
Version 5 (8.1.0 release)
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Version 4 (7.13.0 release)
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Version 3 (7.12.0 release)
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Version 2 (7.11.2 release)
  • Formatting only