Microsoft Defender AV must use advanced protection against ransomware.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-278650	SRG-APP-000210	WNDF-AV-000046	SV-278650r1144036_rule	2025-11-25	2

Description
This policy setting provides an extra layer of protection against ransomware. It uses both client and cloud heuristics to determine whether a file resembles ransomware. This rule doesn't block files that have one or more of the following characteristics: - The file is found to be unharmful in the Microsoft cloud. - The file is a valid signed file. - The file is prevalent enough to not be considered as ransomware. - The rule tends to err on the side of caution to prevent ransomware.

Description

This policy setting provides an extra layer of protection against ransomware. It uses both client and cloud heuristics to determine whether a file resembles ransomware. This rule doesn't block files that have one or more of the following characteristics: - The file is found to be unharmful in the Microsoft cloud. - The file is a valid signed file. - The file is prevalent enough to not be considered as ransomware. - The rule tends to err on the side of caution to prevent ransomware.

ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\Windows Defender Exploit Guard\ASR\Rules Criteria: If the value "c1db55ab-c21a-4637-bb3f-a12568109d35" is REG_SZ = 1, this is not a finding. If the value is other than 1, this is a finding.

ℹ️ Check

Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\Windows Defender Exploit Guard\ASR\Rules Criteria: If the value "c1db55ab-c21a-4637-bb3f-a12568109d35" is REG_SZ = 1, this is not a finding. If the value is other than 1, this is a finding.

✔️ Fix
Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules to "Enabled". Under the policy option "Set the state for each ASR rule:", then click "Show". Enter GUID "c1db55ab-c21a-4637-bb3f-a12568109d35" in the "Value Name" column. Enter "1" in the "Value" column. Click "OK". Click "Apply".

✔️ Fix

Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Microsoft Defender Exploit Guard >> Attack Surface Reduction >> Configure Attack Surface Reduction rules to "Enabled". Under the policy option "Set the state for each ASR rule:", then click "Show". Enter GUID "c1db55ab-c21a-4637-bb3f-a12568109d35" in the "Value Name" column. Enter "1" in the "Value" column. Click "OK". Click "Apply".