Microsoft Defender AV must enable extended cloud check.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-278662	SRG-APP-000210	WNDF-AV-000058	SV-278662r1144061_rule	2025-11-25	2

Description
When Microsoft Defender Antivirus finds a suspicious file, it can prevent the file from running while it queries the Microsoft Defender Antivirus cloud service. The default period that the file is blocked is 10 seconds. Extending the cloud block timeout period can help ensure there is enough time to receive a proper determination from the Microsoft Defender Antivirus cloud service.

ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> MpEngine >> Configure extended cloud check is set to "Enabled" with a Policy Option value of "50"; otherwise, this is a finding. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine Criteria: If the value "MpBafsExtendedTimeout" is REG_DWORD = 50, this is not a finding. If the value is other than 50, this is a finding.

ℹ️ Check

Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> MpEngine >> Configure extended cloud check is set to "Enabled" with a Policy Option value of "50"; otherwise, this is a finding. Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine Criteria: If the value "MpBafsExtendedTimeout" is REG_DWORD = 50, this is not a finding. If the value is other than 50, this is a finding.

✔️ Fix
Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> MpEngine >> Configure extended cloud check to "Enabled" with a Policy Option value of "50". Click "OK". Click "Apply".