Microsoft Defender AV must configure local administrator merge behavior for lists.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-278656	SRG-APP-000210	WNDF-AV-000052	SV-278656r1144051_rule	2025-11-25	2

Description
This policy setting configures how locally defined lists are combined or merged with globally defined lists. This setting applies to exclusion lists, specified remediation lists, and attack surface reduction.

ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Configure local administrator merge behavior for lists 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 Criteria: If the value "DisableLocalAdminMerge" is REG_DWORD = 1, this is not a finding. If the value is 0, this is a finding.

ℹ️ Check

Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Configure local administrator merge behavior for lists 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 Criteria: If the value "DisableLocalAdminMerge" is REG_DWORD = 1, this is not a finding. If the value is 0, this is a finding.

✔️ Fix
Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Configure local administrator merge behavior for lists to "Enabled". Click "OK". Click "Apply".