Microsoft 365 Exchange Safe Attachment Rule Disabled

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: 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/disable-safeattachmentrule?view=exchange-ps

Tags:

Domain: Cloud
Data Source: Microsoft 365
Use Case: Configuration Audit
Tactic: Defense Evasion

Version: 206

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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Setup

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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:"Disable-SafeAttachmentRule" and event.outcome:success

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Impair Defenses
- ID: T1562
- Reference URL: https://attack.mitre.org/techniques/T1562/

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