Windows Defender

Protecting Windows 11 against viruses, malware, and other electronic attacks requires a combination of common sense and using and relying on the system's built-in security tools. Key among the latter is a service called Windows Defender.

Windows Defender provides protection from online threats such as viruses, malware, and ransomware. But the best things about this service, perhaps, are that it's free, effective, and automatic. It comes with Windows 11, works in the background, and is always enabled, and it will occasionally display a notification just to let you know it's doing its thing.

Scan a file or folder with Windows Defender
While Windows Defender usually works without any intervention, you may occasionally want to perform a manual scan of a file (or a group of files), a folder (or a group of folders) or even the entire PC.

To scan one or more files or folders---a suspicious file, perhaps---navigate to the appropriate destination with File Explorer, select the item(s) in question, right-click, choose "Show more options," and then select "Scan with Windows Defender" from the context menu that appears.

The Windows Security app opens to the Virus & threat protection page and runs what's called a custom scan on the selected items. This typically happens so quickly that you will likely miss it.

Scan your PC with Windows Defender
If you open Windows Security and navigate to Virus & threat protection, you can also run a quick, full, or custom scan of your entire PC using the Quick scan button.

Select the type of scan you want and click "Scan now" to do so.

Select "Microsoft Defender Antivirus (offline scan)" to perform an offline scan of your PC outside of Windows. This option requires the PC to reboot and can take a long time.