The best way to check your PC for malware

When you think of a computer infected by malware, you might envision flashing pop-ups all over the screen or other obvious signs. And while these can happen today (like with ransomware), most modern computer attacks are more sinister and subtle. They want to avoid detection so they can capture your sensitive information and otherwise play the long game.

Still, you might suspect malware if your PC is suddenly running slowly, freezes more often than usual or you notice strange processes running. Whether you think your computer has a security issue or you just want to run a scan for peace of mind, it's not difficult to check your PC for malware. You can get several opinions from different tools, too.

Windows 11 has built-in protection through Microsoft Defender, an antivirus tool that's part of the Windows Security suite. Search for that app using the Start menu to check out everything it offers. Each icon will show a green checkmark if all is well; if there are concerns, you'll see yellow or red warning icons depending on their severity.

For our purposes, the Virus & threat protection section is most relevant. Microsoft Defender is turned on by default and scans regularly to check for threats, with details of the latest one shown at the top. Click Allowed threats to see which flagged items you've approved; if you see something here you don't recognize, this can give you a clue to issues on your system. Also check the Protection history tab, which logs when Windows Defender takes action.

Defender's quick scans only look "where threats are commonly found." To go deeper, choose Scan options followed by Full scan > Scan now. This can take some time depending on how many files you have on your system. The Microsoft Defender Antivirus (offline scan) option restarts your PC to put it into the Windows Recovery Environment, where a scan is more likely to find malicious threats that try to cloak themselves. Give it a try if something still feels off after a full scan.

Also inside Windows Security, select the Firewall & network protection entry and make sure the firewall is turned on for all three types of connections. While you can get much more granular with which apps are allowed through the firewall, the default options (blocking incoming connections you haven't given permission for) are good in most cases. Understanding how a VPN works can add another layer of protection to your connection if you're interested.

Windows' built-in security tools are a solid baseline for blocking incoming threats and finding any that do get through. But it's smart to have at least one other anti-malware scanner (not a second real-time antivirus) that can catch what Defender might miss. One of the best is Malwarebytes, which I've used for many years. Its free version offers an on-demand scanner, which you can run when you suspect something or every so often as part of your regular security checks.

Like with Defender, you can do a Quick Scan to check the areas where threats most often live, a Custom Scan to choose exactly where the tool searches or a Deep Scan for a comprehensive look that will likely slow your system down for a while. If Malwarebytes finds anything, it will alert you and give options for dealing with the threats (like quarantining or deleting them). Malwarebytes also offers a separate free tool called AdwCleaner, which focuses on adware and similar junk. It's worth giving it a try if you're fighting something other tools weren't able to remove.

If you're interested in more proactive protection, Malwarebytes has several paid subscriptions that offer real-time protection against threats, as well as scam-blocking features in your browser (and more for the higher-tier plans). While these can help, they aren't usually necessary if you browse carefully, as we'll discuss in a moment.

In case you need to get more advanced in your fight against infection, there are further options to try. Entering safe mode on your computer before running scans (with whatever anti-malware tools you have installed) can help since it's a simplified environment without a network connection. Microsoft also updates and runs its Malicious Software Removal Tool each month, which is designed to detect and remove common forms of malware. To run this manually, press Win + R to open the Run dialog, enter "wrt" and confirm the UAC prompt to open it.

Other second-opinion tools include ESET Online Scanner and Emsisoft Emergency Kit. VirusTotal is also a strong companion tool to check files or webpages for infection.

You almost certainly don't need a third-party antivirus to replace Windows Defender. While these tools can provide good protection for free, most have constant pop-ups nagging you to upgrade to the paid version, which is not necessary. The subscription plans add extras like password managers and VPNs, but you can find free or superior tools elsewhere. Microsoft has a natural incentive to keep Defender strong: If it does a poor job, Windows is less secure by default, resulting in bad press and fewer people wanting to use it. In contrast, third-party AV companies primarily make money when you upgrade.

If scans from Windows Defender, Malwarebytes and any other tools you run come back negative, your PC is likely clean. For the future, it's always better to keep threats away from your device in the first place instead of having to clean them up. Be aware of common attack methods like random email attachments, shady download sites and fake security warnings.

It's also worth remembering that antivirus tools can't protect you from all digital threats. A Malwarebytes scan won't stop someone from breaking into your Google account because you use a weak password, for example. Some security suites warn you if you open a phishing site, but they can't know about all of them. And PC protection tools can't prevent you from falling for a gift card scam over the phone.

Follow crucial tips for online safety, and you hopefully won't have to worry about malware removal or any other threats often.