The reason is because Windows Defender is set to run a scan every day at a random time. If this is the first time you’re opening up Windows Defender, you may notice a scan has already been done and wonder how that happened. This gives you when the last scan took place. While on the Home screen, you may also notice the Scan details at the bottom.

This is where you’d choose Custom and browse to that folder. Perhaps you’ve downloaded something and want to ensure it’s safe. The Custom option is there if you know the exact folders you’d like to scan. Custom Scansįinally, you have the Custom option. It will take much longer but will do a more thorough scan. Full will interrogate every file on your computer that’s not explicitly excluded. However, if you have the time or might be leaving your computer for a while, I suggest choosing Full. This will detect and remove malware in places like temp directories, browser caches, and so on. If you just want Windows Defender to scan for malware that’s in the “usual” places as defined by Microsoft, choose Quick. In the Scan options box, you’ll have a Quick, Full, and Custom scan options.

To do that, head back to the Home tab again, and this time you’ll notice the Scan options box. Once you’ve configured Windows Defender to your liking and have ensured it’s up to date, then, and only then, can you kick off a scan. Once here, click on Update definitions to get the latest virus definitions from Microsoft.

Once you’ve reviewed the settings, head back to the home screen, and click on Update. In the Add an Exclusion box, you can pick and choose files, entires folder, have Windows Defender match files by extension and even exclude all files associated with a process. I’ve personally seen times where antivirus has killed Exchange and DHCP MDB databases! The Settings window gives you a few options with the most important one being able to exclude files if, for some reason, you have applications that don’t play nice with antivirus/antimalware scanning.

Windows defender periodic scanning