Microsoft Defender AV must be configured to scan all downloaded files and attachments.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-213444	SRG-APP-000209	WNDF-AV-000020	SV-213444r823060_rule	2022-04-08	2

Description
This policy setting allows configuration of scanning for all downloaded files and attachments. If this setting is enabled or not configured, scanning for all downloaded files and attachments will be enabled. If this setting is disabled, scanning for all downloaded files and attachments will be disabled.

ℹ️ Check
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Microsoft Defender Antivirus >> Real-time Protection >> "Scan all downloaded files and attachments" is set to "Enabled" 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 "DisableIOAVProtection" 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 >> "Scan all downloaded files and attachments" is set to "Enabled" 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 "DisableIOAVProtection" 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 >> "Scan all downloaded files and attachments" to "Enabled" or "Not Configured".