IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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Microsoft 365 Exchange Malware Filter Policy Deletion

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Microsoft 365 Exchange Malware Filter Policy Deletion

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Identifies when a malware filter policy has been deleted in Microsoft 365. A malware filter policy is used to alert administrators that an internal user sent a message that contained malware. This may indicate an account or machine compromise that would need to be investigated. Deletion of a malware filter policy may be done to evade detection.

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:

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

Tags:

Elastic
Cloud
Microsoft 365
Continuous Monitoring
SecOps
Configuration Audit

Version: 7 (version history)

Added (Elastic Stack release): 7.11.0

Last modified (Elastic Stack release): 8.4.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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A malware filter policy may be deleted 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:"Remove-MalwareFilterPolicy" and
event.outcome:success

Threat mapping

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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/

Rule version history

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Version 7 (8.4.0 release)

Formatting only

Version 5 (8.1.0 release)

Formatting only

Version 4 (7.13.0 release)

Formatting only

Version 3 (7.12.0 release)

Formatting only

Version 2 (7.11.2 release)

Formatting only

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