Microsoft’s built-in anti-malware software used to be thought of as totally worthless, but these days, it can hang with big names like Kaspersky and Avast in independent tests ( blocking 99.7% of threats). Searching “Windows Defender” in the Start menu will bring up Windows Security, and even now, Microsoft often refers to its actual antivirus scanning as Windows Defender. Once upon a time, Windows Security was called Windows Defender Security Center, but the app is largely similar. If you think your PC is infected with some kind of malware or you just want to do a scan as part of a digital cleanup, Windows has a built-in security tool that can help you on your way - no third-party software to install or pay for.