Microsoft 365 Exchange Safe Attachment Rule Disabled

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Microsoft 365 Exchange Safe Attachment Rule Disabled

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Identifies when a safe attachment rule is disabled in Microsoft 365. Safe attachment rules can extend malware protections to include routing all messages and attachments without a known malware signature to a special hypervisor environment. An adversary or insider threat may disable a safe attachment rule to exfiltrate data or evade defenses.

Rule type: query

Rule indices:

  • filebeat-*
  • logs-o365*

Severity: low

Risk score: 21

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: 2 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 7.11.2

Rule authors: Elastic

Rule license: Elastic License

Potential false positives

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A safe attachment rule may be disabled 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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The Microsoft 365 Fleet integration or Filebeat module must be enabled to use this rule.

Rule query

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

Threat mapping

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Framework: MITRE ATT&CKTM

Rule version history

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Version 2 (7.11.2 release)
  • Formatting only