Windows Defender AV must be configured to run and scan for malware and other potentially unwanted software.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-75153	WNDF-AV-000004	SV-89833r5_rule		High

Description
This policy setting turns off Windows Defender Antivirus. If you enable this policy setting Windows Defender Antivirus does not run and computers are not scanned for malware or other potentially unwanted software. When the setting is Disabled and a third-party antivirus solution is installed, the two applications can both simultaneously try to protect the system. The two AV solutions both attempt to quarantine the same threat and will fight for access to delete the file. Users will see conflicts and the system may lock up until the two solutions finish processing. When the setting is Not Configured and a third-party antivirus solution is installed, both applications co-exist on the system without conflicts. Defender Antivirus will automatically disable itself and will enable if the third-party solution stops functioning. When the setting is Not Configured and Defender Antivirus is the only AV solution, Defender AV will run (default state) and receive definition updates. An administrator account is needed to turn off the service. A standard user cannot disable the service.

Description

This policy setting turns off Windows Defender Antivirus. If you enable this policy setting Windows Defender Antivirus does not run and computers are not scanned for malware or other potentially unwanted software. When the setting is Disabled and a third-party antivirus solution is installed, the two applications can both simultaneously try to protect the system. The two AV solutions both attempt to quarantine the same threat and will fight for access to delete the file. Users will see conflicts and the system may lock up until the two solutions finish processing. When the setting is Not Configured and a third-party antivirus solution is installed, both applications co-exist on the system without conflicts. Defender Antivirus will automatically disable itself and will enable if the third-party solution stops functioning. When the setting is Not Configured and Defender Antivirus is the only AV solution, Defender AV will run (default state) and receive definition updates. An administrator account is needed to turn off the service. A standard user cannot disable the service.

STIG	Date
MS Windows Defender Antivirus Security Technical Implementation Guide	2020-05-12

Details

Check Text ( C-74945r6_chk )
Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Windows Defender Antivirus >> "Turn off Windows Defender Antivirus" is set to “Not Configured”. For Windows 10: Procedure: Use the Windows Registry Editor to navigate to the following key: HKLM\Software\Policies\Microsoft\Windows Defender Criteria: If the value "DisableAntiSpyware" does not exist, this is not a finding. For Windows Server 2016/Windows Server 2019: Note: This only applies when a third-party antivirus solution is enforced on the system. Due to changes from Microsoft in the Server 2016/Server 2019 architecture, Windows Defender Antivirus will not disable itself when other antivirus products are detected. Microsoft has also removed API's for other Antivirus software to cleanly stop and disable Windows Defender AV. This was a design choice by Microsoft to maximize protection in Server 2016/Server 2019. If there is a third-party antivirus product enforced on the system, the Windows Defender Antivirus must be uninstalled. Procedure: Access Add Roles and Features Wizard >> Features Criteria: If “Windows Defender Features (Installed) is selected, this is a finding.

Check Text ( C-74945r6_chk )

Verify the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Windows Defender Antivirus >> "Turn off Windows Defender Antivirus" is set to “Not Configured”.

For Windows 10:
Procedure: Use the Windows Registry Editor to navigate to the following key:
HKLM\Software\Policies\Microsoft\Windows Defender

Criteria: If the value "DisableAntiSpyware" does not exist, this is not a finding.

For Windows Server 2016/Windows Server 2019:
Note: This only applies when a third-party antivirus solution is enforced on the system.
Due to changes from Microsoft in the Server 2016/Server 2019 architecture, Windows Defender Antivirus will not disable itself when other antivirus products are detected. Microsoft has also removed API's for other Antivirus software to cleanly stop and disable Windows Defender AV. This was a design choice by Microsoft to maximize protection in Server 2016/Server 2019.

If there is a third-party antivirus product enforced on the system, the Windows Defender Antivirus must be uninstalled.

Procedure: Access Add Roles and Features Wizard >> Features

Criteria: If “Windows Defender Features (Installed) is selected, this is a finding.

Fix Text (F-81765r5_fix)
For Windows 10: Set the policy value for Computer Configuration >> Administrative Templates >> Windows Components >> Windows Defender Antivirus set "Turn off Windows Defender Antivirus" to "Not Configured". For Windows 2016/Windows 2019: Use the following PowerShell cmdlet to uninstall Windows Defender AV on Windows 2016/Windows 2019: Uninstall-WindowsFeature -Name Windows-Defender