Windows Defender is a free program that Microsoft includes with Windows 10. It protects your computer from spyware, viruses and other malware (i.e., malicious software that harms your device). It used to be called "Microsoft Security Essentials." It's turned on by default when you first start up Windows 10, but Windows Defender can be turned off. One important note is that if you install another antivirus program, you should disable Windows Defender. Antivirus programs don't like being installed on the same machine and can confuse your computer.
To learn how to set up and use Windows Defender, you first need to find it. The easiest way is to type "defender" in the search window at the bottom left of the taskbar. The window is next to the Start button.
When Windows Defender opens, you'll see this screen. The first thing to notice is the color. A yellow bar at the top computer monitor here, along with the exclamation point, is Microsoft's not-too-subtle way of telling you that you need to take some action. Notice that it ways "PC status: Potentially unprotected" at the top, in case you missed all the other warnings.
In this case, the text tells us that we need to run a scan. Underneath, the check marks tell us that "Real-time protection" is on, meaning that Defender is continuously running and that my virus definitions are "Up to date." That means Defender has the latest descriptions of viruses loaded and should be able to recognize the latest threats to the computer.
There's also a Scan now button, to manually kick off a scan, and below that, the details of my last scan, including what kind it was.
To the right are three scan options. Let's go through them. (Also note that the phrase "Scan options" is only partially visible. This appears to be a glitch in the program, so don't worry about it.)
Quick scan-This checks the areas that malware is most likely to reside. It's not as thorough as a full scan but is much faster. It's usually enough to keep you safe.
Full scan-This scan checks everything on your hard drive. It's slow, and can take a long time, but is more likely to find a bit of malware hiding in an unexpected place.
Custom scan-You can pick and choose the files and places you want to scan. Leave this alone unless you're a high-level user.