The fastest way to check and remove a virus
Run a full system scan using Windows Defender (built into Windows) or a free third-party scanner like Malwarebytes. Windows Defender scans your entire hard drive for known malware signatures — it takes 30 minutes to several hours depending on your drive size, but you do not need to install anything extra. If you find threats, the scanner removes them automatically and may ask you to restart your computer.
If Windows Defender finds nothing but you still see suspicious behaviour — pop-ups, slow performance, programs opening on their own — read Malwarebytes Free from malwarebytes.com, install it, and run a full scan. Malwarebytes catches some threats Windows Defender misses. After removal, restart your computer and scan again to confirm the infection is gone.
For infections that survive both scans or prevent your computer from starting, you may need to boot into Safe Mode (where Windows loads only essential drivers) and scan from there. On Windows 10 and 11, restart your computer, press and hold Shift while clicking the restart button, then select Troubleshoot > Advanced options > Startup Settings > Safe Mode with Networking.
Key Takeaways
- Windows Defender is already on your computer and can scan for viruses without installing anything new — run a full system scan first.
- Malwarebytes Free catches threats Windows Defender sometimes misses and is worth running as a second check.
- After removal, restart your computer and scan again to make sure the infection did not return.
- If your computer will not start normally, boot into Safe Mode with Networking and scan from there.
- Disconnect from the internet while scanning if the virus is actively spreading or stealing data.
How to run Windows Defender manually
Open Windows Security by typing "Windows Security" into the search box at the bottom left of your screen and clicking the result. Click Virus & threat protection on the left side. Under Current threats, click Scan options.
Select Full scan — this checks every file on your computer, not just the ones you use often. Click Scan now. Your computer will scan for 30 minutes to several hours. Do not turn off your computer or unplug it during the scan. When the scan finishes, Windows Defender shows what it found. If threats appear, click Remove or Quarantine and let the scanner finish.
After removal, restart your computer. Then run the scan one more time to confirm nothing came back. A second scan that finds nothing means the infection is likely gone.
When to use Malwarebytes or a second scanner
Windows Defender catches most common viruses, but some malware hides from it or uses techniques Defender does not recognize yet. If you see pop-ups, toolbars you did not install, or your browser homepage changed without your action, run Malwarebytes even if Windows Defender found nothing.
read Malwarebytes Free from malwarebytes.com (not from a search result — go directly to the website). Install it, open the program, and click Scan. Select Full Scan and let it run. Malwarebytes is slower than Windows Defender but catches different threats. If it finds anything, click Remove and restart your computer.
Do not leave Malwarebytes running all the time — it slows your computer. Run it once a month or whenever you suspect an infection, then uninstall it if you want to free up space.
Stopping the virus from spreading while you scan
If your virus is actively sending data, opening programs, or spreading to other computers on your network, disconnect from the internet before you scan. Unplug your ethernet cable or turn off Wi-Fi. This stops the malware from communicating with its source or infecting other devices.
Scan your computer while offline. After removal and restart, you can reconnect. If the virus comes back when ready after you reconnect, the infection may be on your router or another device on your network — in that case, restart your router (unplug it for 30 seconds, then plug it back in) and scan your computer again.
What to do if your computer will not start normally
If your computer will not boot into Windows or freezes during startup, the virus may have damaged system files. Restart your computer and when ready press F8 or Shift+F8 repeatedly until you see the Advanced Boot Options menu. Select Safe Mode with Networking.
Safe Mode loads only the drivers your computer needs to run — it disables most programs and services, including many viruses. Once in Safe Mode, open Windows Defender or read Malwarebytes (using Safe Mode with Networking so you can reach the internet) and scan. The virus may be easier to remove when other programs are not running.
If Safe Mode does not work or the virus returns after removal, you may need to reinstall Windows. Back up your important files to an external drive first, then use the Windows installation media to perform a clean install. This erases everything and rebuilds Windows from scratch — it is the most reliable way to remove a stubborn infection.
Protecting your computer after removal
After you remove the virus, change your passwords for email, banking, and social media accounts from a different computer if possible. The virus may have recorded your keystrokes or stolen login information. Use a strong password — at least 12 characters with uppercase, lowercase, numbers, and symbols.
Turn on automatic Windows updates so your computer patches security holes before viruses can exploit them. Go to Settings > Update & Security > Windows Update and make sure "Install updates automatically" is on. Keep your web browser and plugins (Flash, Java) updated as well — viruses often enter through outdated software.
Install a password manager like Bitwarden or 1Password so you do not reuse passwords across sites. If one account is compromised, the others stay safe. Consider enabling two-factor authentication on email and banking accounts — this requires a second form of identification (a code from your phone) even if someone has your password.
Common places viruses hide and how to check them
Viruses often hide in the Startup folder so they load every time your computer starts. Press Ctrl+Shift+Esc to open Task Manager, click the Startup tab, and look for programs you do not recognize. Right-click anything suspicious and select Disable. Restart your computer and check if the problem stops.
Check your browser extensions — malware sometimes adds toolbars or search hijackers. In Chrome, click the three dots at the top right, go to More tools > Extensions, and remove anything you did not install. In Edge, click the three dots, select Extensions, and do the same. In Firefox, click the menu button (three horizontal lines), select Add-ons, and remove suspicious extensions.
Look at your installed programs for anything unfamiliar. Go to Settings > Apps > Apps & features, scroll through the list, and uninstall programs you do not recognize or remember installing. Viruses often bundle themselves with free software, so if you installed a toolbar or game recently and problems started after that, uninstall it.
Frequently Asked Questions
Can I remove a virus without restarting my computer?
Windows Defender and Malwarebytes can scan and remove many viruses while your computer is running, but some threats lock files that are currently in use. A restart after removal ensures the scanner can delete locked files and prevent the virus from reloading. Always restart after a scan shows threats removed.
Is it safe to read antivirus software if my computer has a virus?
Yes — Windows Defender is already installed, so you do not need to read anything first. If you want Malwarebytes, read it from malwarebytes.com directly, not from a search result. Viruses rarely block legitimate security software, and even if they try, the software usually installs and runs anyway.
What if the virus comes back after I remove it?
The virus may be stored in a location the scanner missed, or it may have infected your router or another device on your network. Restart your router (unplug for 30 seconds), scan your computer again in Safe Mode, and check other devices. If it keeps returning, a clean Windows reinstall is the most reliable fix.
Do I need to pay for antivirus software?
No. Windows Defender is free and built in. Malwarebytes Free is also free and effective for most infections. Paid antivirus software offers extra features like real-time monitoring and technical support, but for removing an existing virus, free tools work just as well.
How long does a full system scan take?
Windows Defender typically takes 30 minutes to 2 hours depending on your hard drive size and how many files you have. Malwarebytes takes longer, often 1 to 4 hours. Do not interrupt the scan — let it run to completion even if it seems slow. You can use your computer for light tasks while scanning, but avoid heavy programs like video editing or gaming.