Learn how to Turn On, Enable or Start Windows Defender manually on a Windows computer. If it doesn't help, you may need to troubleshoot the issue.

If you happen to be a Windows Insider, you can test out the Windows Defender Security Center now by finding it under "All Apps" in the start menu of the latest preview build.

Here’s how it works. Windows Defender, an already powerful PC-protection tool before the release of the Creators Update, has been transformed into the Windows Defender Security Center.

Admins can enable Controlled folder access via the Windows Defender Security Center, Group Policy, PowerShell, or via a mobile device management configuration service provider.

In this release, the Controlled Folder Access feature does not work with third-party antivirus software. With those prerequisites out of the way, open Windows Defender Security Center.