How to scan your Windows PC for malware

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. It’s called Windows Security.

Once upon a time, Windows Security was called Windows Defender Security Center, but the app is largely similar. 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.

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). Microsoft has also been pushing security with Windows 11, even going so far as to confusingly lock out people with older computers that don’t have certain hardware. But when it comes to good old-fashioned software security, Windows 11 is relatively simple.

To open it, you can simply type “Windows Security” into the Start menu search. You can also get to it by going to “Settings” > “Privacy & Security” > “Windows Security,” which will give you a quick overview of your system’s status. You can then click the “Open Windows Security” button to get access to the full app.

After you’ve got it open, here’s some of what you can do:

Run a malware scan on Windows 11

By default, Windows’ built-in security will run in the background and attempt to immediately block any malicious files that make their way to your computer. However, if you want to do periodic spot checks, you can manually run a scan.

To do this, go to “Windows Security” > “Virus & threat protection,” and click the “Quick scan” button. If you want to do a more thorough scan, which will take longer but will check all your files and running programs, you can instead click the “Scan options” button, and choose “Full scan.”

If Windows finds malware during the scan, you can click the “Start actions” button to begin the process of removing the virus(es) from your computer.

If the scan doesn’t turn up anything, you’ll just see a report about how long the scan took, how many files were scanned, and when the scan took place.

Keep Windows security up to date

If you want to make sure Windows is always scanning for viruses in the background, you can go to “Windows Security” > “Virus & threat protection” > “Virus and threat protection settings.” Click on “Manage settings” and make sure the “Real-time protection” option is toggled on.

To make sure your computer is using the latest antivirus definitions, you can go to “Windows Security” > “Virus & threat protection” > “Virus & threat protection settings.” Click on “Manage settings” and make sure “Cloud-delivered protection” is toggled on.

Windows 11 generally does its best to keep itself updated, but to manually check, you can go to “Settings” > “Windows update,” which can be found both at the bottom left and top right. From there, you can click the “Check for updates” button. You can also type “check for updates” in the Start menu search bar to be taken directly to the “Windows Update” screen.

If you’ve installed a lot of apps from the Microsoft Store, you can update those as well by opening the Microsoft Store, going to “Library” (on the bottom left of the window), then clicking the “Get Updates” button.

If you still have Windows 10

If you’re running the latest version of Windows 10, the process for running a virus scan will be largely the same as on Windows 11. On some older versions of Windows 10, you’ll use the Windows Defender Security Center application instead, but the process will be much the same after you open the app.

What are the signs my PC is infected?

Malware comes in many shapes and forms, but there are some common things it may do to your computer. If you notice that your search engine, browser homepage, or even desktop wallpaper have changed without you doing anything, it may be time to run a scan as described above. Other symptoms could be your computer running hotter or slower than usual or seeing popups or notifications that you haven’t seen before.

Google has a great video describing some of the common symptoms of malware.

If Windows detects a threat

If you get a notification from the Microsoft Security app saying that it’s detected a threat, it’s likely that the problem has already been dealt with. However, it is worth double-checking the notification — some malware (especially malicious web ads) will pretend to be an antivirus notification to get you to click on them.

Windows Security notifications will look like the image shown below and will appear on the top right corner of your screen. After they disappear, they’ll be shown on the notification screen, which you can view by clicking on the clock in your taskbar.

Whitelisting a file

While anti-malware software tries its best to only flag the bad files and leave the good ones, sometimes it will get it wrong. If you’re very sure that Windows has made a mistake and deleted a file that it shouldn’t have, you can retrieve it.

Before you do so, it’s worth noting that just because you trust the person who sent you a file does not mean that the file is safe. There is some malware that is able to hijack people’s emails and send copies to everyone in their contacts. If you receive a suspicious file from someone you trust, it’s a good idea to ask them about it before trying to open it.

To view and restore an incorrectly flagged file, go to “Windows Security” > “Virus and threat protection” > “Protection history.” There you’ll find any threats that Windows Security found, along with their severity level. To restore a file (which, again, you should be very careful before doing), click on the entry, then click the “Actions” button to get access to the “Allow” button.

What happens after you allow the file depends on how it was dealt with. If its status is “Quarantined,” allowing it will put it back on your computer. If its status is “Removed,” you’ll have to download it again, but Microsoft Security won’t stop you.

You can view a list of the detected files you’ve allowed by going to “Windows Security” > “Virus & threat protection” > “Allowed threats.” If you’ve decided they are indeed a threat, you can re-delete them by clicking on them, then clicking the “Don’t allow” button.

When things get nasty

Sometimes there are viruses or pieces of malware that fight back when you try to remove them. To help deal with this, Windows has a sort of extra-strength version of its antivirus scan. To run it, go to “Windows Security” > “Virus & threat protection” > “Scan options,” and select “Microsoft Defender Offline scan.” After clicking the “Scan now” button, your computer will restart into a special mode to do a scan. Once it’s done, your computer will restart again, bringing you back to Windows.

If your computer still shows signs of being infected, some of us here at The Verge recommend the free version of Malwarebytes, which has saved our (and our relatives’) machines more than a few times. (It’s a good idea to have Malwarebytes already on your computer since some malware can block you from installing any additional security apps.)

If your PC is still locked up, or you’re suddenly getting notifications that you need to send somebody money to unlock it, it may be time to contact an IT professional.

Third-party anti-malware apps

While Windows Security should do a good job at protecting your computer from viruses, malware, and other nasty files, there are still things it can’t do — for instance, even with Windows 11, the built-in tools won’t protect you from email phishing scams or from scam ads in your web browser.

If you’re looking to step up your game from the basic Windows Security, you might want to check out anti-malware suites, such as McAfee, Norton 360, Kaspersky or Bitdefender. Searching out a few reviews will give you a good idea of what you need (and what you don’t — looking at you, programs that come with crypto miners).

If you’ve heard about the dangers of running multiple anti-malware systems, don’t worry; Microsoft says its built-in solution will automatically turn off if it detects that there’s another antivirus installed and activated. If you uninstall the other anti-malware app, Microsoft’s should turn back on automatically.