Microsoft Defender AV must enable heuristics.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-278680	SRG-APP-000278	WNDF-AV-000077	SV-278680r1144083_rule	2025-11-25	2

Description
Always-on protection consists of real-time protection, behavior monitoring, and heuristics to identify malware based on known suspicious and malicious activities.

ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Scan >> Turn on heuristics is set to "Enabled"; otherwise, this is a finding. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\Scan Criteria: If the value "DisableHeuristics" is REG_DWORD = 0, 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 >> Scan >> Turn on heuristics is set to "Enabled"; otherwise, this is a finding. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\Scan Criteria: If the value "DisableHeuristics" is REG_DWORD = 0, 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 >> Scan >> Turn on heuristics to "Enabled". Click "OK". Click "Apply".