Microsoft Windows 10 has a preloaded antivirus software named Microsoft Defender. It scans for malware in the background, but you can also perform a full-system scan.

.

1. Open Start menu (i.e. Windows key) and type “Windows Security.” 

2. Click on the “Windows Security” app icon that pops up.

3. Open Start and type Windows Security on Windows 10

4. In the sidebar, click “Virus & Threat Protection.”

Note: It’s possible to do a quick scan from here by clicking the Quick Scan button, but if you haven’t scanned recently, consider doing a deeper scan. 

5. In the area below the Current Threats heading, click Scan Options.

In the Scan Options menu, you will see a list of four different types of scans you can perform on your computer using Microsoft Defender.

- Quick Scan: Scans folders in your system where threats are usually found, such as the Downloads and Windows folders. This usually only takes a few minutes to complete.

- Full Scan: This scans every file on your computer and all running programs as well. The scan may take longer than an hour to complete.

- Custom Scan: If you choose this option, Windows Security will ask you for a specific file or folder location that you’d like to scan.

- Microsoft Defender Offline Scan: This option restarts your machine and scans system files and programs while they are not running, which is useful if a piece of malware is currently running and potentially interfering with the scan.

If you think your PC has been compromised, start with a Full scan. 

6. Select Full Scan” and click the Scan Now button.

A full-system scan will begin, and Windows Security will show a progress indicator bar.

When the scan is complete, you’ll see the results. If everything was okay, you’ll see a message that says “No Current Threats.”

However, if the scan did find some malware, you will see a message that says “Threats Found” and a list of the infected files just below.

To remove the threats, click the “Start Actions” button.

After clicking Start Actions, Microsoft Defender will remove the threats automatically. If you’d like to see details on what threats were removed, click Protection History on the same page.

Note: If Defender found a threat during a Quick or Full scan, it's wise to choose “Microsoft Defender Offline Scan” on the Scan Options screen and run it immediately afterward... Just in case.

You're all done!