There is no need to install any security suite in Windows 10, since Windows Defender is there. This built-in antivirus is enough capable to provide you primary protection for your device and keep you stay safe plus updated.
However, if your system is part of domain and if you’re domain controller has assigned some policies, Defender may got block. While in some cases, if you’ve installed another antivirus previously, it will have blocked Defender. The block may remain intact even if you’ve remove third-party antivirus program. In such condition, when you try to open Windows Defender, you’ll get following message instead:
This app is turned off by Group Policy
If you’re using another app to check for malicious or unwanted software, use Security and Maintenance to check that app’s status.
To allow this app to run, contact your security administrator to enable the program via group policy.
If you’re the administrator of an isolated machine on which this issue is appearing, you can easily fix it via below mentioned steps. In case if your system is part of domain, contact your administrator and ask them to unblock Windows Defender via Group Policy.
FIX : “This App Is Turned Off By Group Policy” For Windows Defender
1. Press + R and put gpedit.msc in Run dialog box to open Local Group Policy Editor. Click OK.
2. Next, in the Local Group Policy Editor window, navigate here:
Computer Configuration -> Administrative Templates -> Windows Components -> Windows Defender
3. At this Group Policy path, making Windows Defender folder highlighted in left pane (refer above shown window) and in the corresponding right pane, look for the Setting named Turn off Windows Defender. You’ll find that this policy is already set to Enabled which is the root cause of this problem. Double click on it to get this:
4. In the above window, select Not Configured option so that it will enable or activate Windows Defender. Click Apply followed by OK. Close the Group Policy Editor. Restart File Explorer via Task Manager and try to open Windows Defender, it should work on.
Hope this helps! Go here if you can’t open Windows Security Center.