12 ways to find viruses on your PC for free (and how to remove them)

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ZDNET’s key takeaways

• Modern antivirus tools have made PC infections rare, but they can still occur.
• Most viruses are designed to go unnoticed, quietly working in the background. 
• Some of the quickest and easiest ways to safeguard your PC are free. 

It’s surprisingly difficult to get your computer infected with a virus these days. Believe me, I’ve tried. Modern antivirus tools have gotten very sophisticated, often stopping threats before they have a chance to do serious damage. Windows Security deserves much of the credit here: I’ve seen the software quickly detect malware and resolve the issue without any user input. There’s a reason I included it in my list of the best antivirus programs for Windows.

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Additionally, you have web browsers with powerful security features and third-party antivirus apps, providing an extra layer of defense. So even if your online safety is less than ideal, you’re fairly well-protected on the internet. That said, just because it’s difficult to get infected doesn’t mean it’s impossible. Cybercriminals of all kinds are constantly developing new ways to steal your information.

But don’t worry, because I’ve got your back. In this guide, I’ll walk you through exactly what to do if your PC gets infected by a virus. Before we dive in, I need to answer one important question.

How do I know if I’ve been infected?

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Fifteen years ago, it was super easy to tell if your computer had a virus. You’d be bombarded from all sides with weird pop-up windows, your desktop would glitch out, and programs would often crash. 

While erratic behavior can still happen, things have changed. Subtlety is the name of the game in 2025. Instead of revealing their presence with visual chaos, many viruses today hide quietly in the background, stealing your data and system’s resources.

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If you suspect something is off, start by opening the Task Manager, then check the Processes tab. Look for any programs using a large amount of processor resources or memory. Ask yourself if you recognize it. If you don’t, there’s a chance it could be malware. Right-click the suspicious software and select End Task.

Other behaviors to look out for, according to the National Cybersecurity Alliance, include:

• Unfamiliar programs and icons littering your desktop
• Missing or corrupted files
• Multiple windows appear and then disappear upon startup
• Lagging browsers
• Frequent error messages
• And, most notably, disabled security settings

That’s right. Norton Antivirus states that disabled security software is a sign that your computer has malware. They’re so bold that they’ll attack your system’s defenses. Keep in mind that ending a process doesn’t remove it. You’ll still need to take further steps to eliminate the problem.

How do I remove viruses?

The first step is to disconnect your PC from the internet to prevent the malware from spreading to other devices. Next, boot into Safe Mode. Safe Mode limits certain background processes, allowing the operating system to be much more stable and less likely to crash. To enter this unique state, restart your computer while holding the Shift key. Upon rebooting, follow this path: Troubleshoot > Advanced options > Startup Settings > Restart.

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After the second restart, press F4 for Safe Mode. Once in Safe Mode, launch Windows Security, and follow this path: Virus & threat protection > Scan options > Full Scan. 

As the name suggests, this performance a deep scan of your system files, which can take an hour or more depending on how much data you have.

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If the infection persists, run a Microsoft Defender Antivirus (offline scan). This option restarts your PC and scans the system during boot-up to detect any hidden malware that may be lurking. It takes about 15 minutes to complete. Alternatively, you can use a trusted third-party antivirus program, such as Malwarebytes. Run a full system scan on your security app of choice. If nothing is found, you’re probably in the clear.

Note: Do not install more than one third-party antivirus software. They’ll conflict with each other and cause performance issues themselves, ironically acting like viruses themselves.

What can I do to better protect myself?

After the worst has passed and you’ve removed the malware, it’s time to strengthen your security so an infection doesn’t happen again. Here are several easy actions you can take to enhance PC protection. Think of this as a lightning round of cybersecurity upgrades:

• Delete temporary files: This clears up system resources and removes any lingering malware. Open Settings, then go to Storage > Temporary files. Select the files you want to delete, and then select Remove files.
• Reset your browser settings: Similar to the previous entry, it’s also important to clear out temporary files in your web browser. This process varies by browsers, but here’s how to do it on Chrome: open Settings via the three-dot menu > Reset settings > Restore settings to their original defaults > Reset settings.
• Uninstall suspicious apps or browser extensions: Cybercriminals will often inside malware inside apps and extensions to slip past Windows’ defenses. Uninstall any unfamiliar software, then delete its remaining files.
• Scan external drives: Malware can linger on connected hardware. While plugged in, open File Explorer, right-click the external device > Show more options > Scan with Microsoft Defender. 
• Install the latest Windows 11 updates: It’s a classic top for a reason; updates patch up security vulnerabilities and improve system protection. Go to Settings > Windows Update and install all available packages.
• Change your login credentials: Use strong, unique passwords or a password manager to secure your account. 
• Avoid suspicious links and attachments: Never click on anything you’re unsure of, whether in emails, messages, or unfamiliar websites. Also, double-check the sender’s email address if you are receiving sensitive files. Scammers often use fake addresses that appear identical to the original to trick you.

If you’re interested in learning more ways to protect yourself, ZDNET has an entire section dedicated to cybersecurity coverage. Here are my top read suggestions to stay one step ahead of threats.

What do I do if a file seems suspicious?

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Let’s say you downloaded a file from an unverified source, such as a random Google Drive account or a sketchy website. You might’ve even pirated a video game or game (no judgment here; I’ve done it many times before). After downloading the files, you get a sinking feeling that the files you downloaded may contain a virus.

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Fortunately, there’s an excellent online tool called VirusTotal that can help. It’s a website that scans and analyzes suspicious files, URLs, domains, and IP addresses to detect any signs of malware. The platform is very reliable, although there have been reports of VirusTotal producing false positives and false negatives.

Simply drag and drop the files onto the website. If it’s safe, the results will appear in green. If it’s malware, the page will turn red with a message stating the content has been flagged by multiple security sources. Assuming it’s the latter, delete the file immediately and empty out your recycle bin.

What do I do if problems persist?

There’s a chance – albeit a small one – that even after running multiple scans, clearing out corrupted files, and uninstalling programs, your PC is still suffering from performance problems. Malware lingers in the deepest reaches of your computer. Perhaps the virus was added to the exclusion list in Windows Security.

Instead of hunting down lingering malware one by one, you’re better off performing a complete reinstallation of Windows 11. ZDNET Senior Contributing Editor Ed Bott has a detailed guide on how to do a clean install of Windows 11, with multiple methods.

Before starting, I strongly recommend backing up important files, like documents, photographs, movies, and browser bookmarks. Ed Bott, once again, has a guide available that’ll help you create a data backup plan. He weighs the pros and cons of external drives and also teaches how to create a system image, among other things. Make sure that you don’t back up or reuse any drivers since they can sometimes carry malware.

Source: Information Technologies - zdnet.com