Emails identified as containing malware SHALL be quarantined or dropped

Contributed by Michael Soule with Jean-Philippe GeorgeAll contributors →

Part of CISA · Exchange Online · Anti-malware · All checks

Run this check

Invoke-Maester -TestId CISA.MS.EXO.10.2

Overview

Emails identified as containing malware SHALL be quarantined or dropped.

Rationale: Email can be used as a mechanism for delivering malware. Preventing emails with known malware from reaching user mailboxes helps ensure users cannot interact with those emails.

Remediation action

1. Sign in to Microsoft 365 Defender.
2. In the left-hand menu, go to Email & Collaboration > Policies & Rules.
3. Select Threat Policies.
4. From the Templated policies section, select Preset Security Policies.
5. Under Standard protection, slide the toggle switch to the right so the text next to the toggle reads Standard protection is on.
6. Under Strict protection, slide the toggle switch to the right so the text next to the toggle reads Strict protection is on.

Note: If the toggle slider in step 5 is grayed out, click on Manage protection settings instead and configure the policy settings according to Use the Microsoft 365 Defender portal to assign Standard and Strict preset security policies to users | Microsoft Learn.

Related links

• Defender admin center - Preset security policies
• Defender admin center - Order and precedence of email protection
• CISA 10 Malware Scanning - MS.EXO.10.2v1
• CISA ScubaGear Rego Reference
• Microsoft Learn - Anatomy of a quarantine policy

Details

Every attribute of this check

Field	Value
Test ID	CISA.MS.EXO.10.2
Severity	High
Suite	CISA
Product	Exchange Online
Related products	Defender
Feature	Anti-malware
Area	Email and collaboration protection
Resource type	Policy
User impact	Low
Implementation cost	Low
MITRE ATT&CK	T1204.002 Malicious File, T1566.001 Spearphishing Attachment
Supports benchmark	CISA SCuBA Secure Configuration Baselines for Microsoft 365 (version ScubaGear main, 2026-10-11), requirement MS.EXO.10.2
Criticality	SHALL
Upstream requirement	Moved to MS.SECURITYSUITE.1.3v1 (was MS.EXO.10.2v1)
Supports controls	cisa-scuba:MS.EXO.10.2, nist-800-53-r5:SI-3
PowerShell test	Test-MtCisaMalwareAction
Services	ExchangeOnline, Graph

Source

• Test: tests/cisa/exchange/Test.CISA.MS.EXO.10.2.ps1
• Documentation: tests/cisa/exchange/Test.CISA.MS.EXO.10.2.md