Microsoft Defender AV must be configured to always enable real-time protection.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-213445	SRG-APP-000278	WNDF-AV-000021	SV-213445r823062_rule	2022-04-08	2

Description
This policy setting turns off real-time protection prompts for known malware detection. Microsoft Defender Antivirus alerts when malware or potentially unwanted software attempts to install itself or to run on your computer. If this policy setting is enabled, Microsoft Defender Antivirus will not prompt users to take actions on malware detections. If this policy setting is disabled or not configured, Microsoft Defender Antivirus will prompt users to take actions on malware detections.

Description

This policy setting turns off real-time protection prompts for known malware detection. Microsoft Defender Antivirus alerts when malware or potentially unwanted software attempts to install itself or to run on your computer. If this policy setting is enabled, Microsoft Defender Antivirus will not prompt users to take actions on malware detections. If this policy setting is disabled or not configured, Microsoft Defender Antivirus will prompt users to take actions on malware detections.

ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Real-time Protection >> "Turn off real-time protection" is set to "Disabled" or "Not Configured". Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection Criteria: If the value "DisableRealtimeMonitoring" is REG_DWORD = 0, this is not a finding. If the value does not exist, this is not a finding. If the value is 1, this is a finding.

ℹ️ Check

Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Real-time Protection >> "Turn off real-time protection" is set to "Disabled" or "Not Configured". Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection Criteria: If the value "DisableRealtimeMonitoring" is REG_DWORD = 0, this is not a finding. If the value does not exist, this is not a finding. If the value is 1, this is a finding.

✔️ Fix
Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Real-time Protection >> "Turn off real-time protection" to "Disabled" or "Not Configured".