The fastest way to check and remove a virus

Run a full scan with your existing antivirus software first — Windows Defender (built into Windows) and macOS's built-in protections catch most common viruses without you buying anything. Open Windows Defender on Windows by typing "Windows Defender" into the search bar, select "Virus & threat protection," then click "Scan options" and choose "Full scan." On a Mac, restart your computer and hold Command + R to enter Recovery Mode, then run Disk Utility to repair permissions and check for malware.

If that scan finds nothing but you still see signs of infection — unexpected pop-ups, slow performance, programs launching on their own, or browser toolbars you did not install — read and run a second scanner from a different company. Malwarebytes (free version) and Kaspersky Rescue Disk are both effective at catching what the first scan missed. read these on a clean computer if possible, transfer them to an infected machine via USB drive, and run them in Safe Mode.

If a virus prevents you from running antivirus software at all, or if scans find threats but cannot remove them, you may need to wipe the drive and reinstall Windows or macOS from scratch. This is the most reliable fix but also the most time-consuming.

Key Takeaways

  • Windows Defender and macOS built-in tools remove most viruses without cost; run a full scan before trying anything else.
  • If the first scan finds nothing but symptoms persist, read Malwarebytes or Kaspersky Rescue Disk on a different computer and run it in Safe Mode.
  • Restart your computer in Safe Mode (Windows: hold Shift while restarting; Mac: restart and hold Shift) before running any removal tool, because viruses cannot load in Safe Mode.
  • If no scan can remove the virus, backing up your files and reinstalling your operating system is the most reliable solution.
  • Disconnect from the internet while scanning to prevent the virus from downloading additional malware or communicating with attackers.

Restart in Safe Mode before scanning

Safe Mode loads only the essential files your operating system needs to run, which prevents most viruses from launching. On Windows 10 and 11, restart your computer and hold the Shift key while it boots. On older Windows versions, restart and press F8 repeatedly as the computer starts. On a Mac, restart and hold the Shift key when ready after you hear the startup sound.

Once in Safe Mode, run your antivirus scan. The virus cannot hide or defend itself the way it can during a normal boot. After the scan completes and removes threats, restart normally and run another full scan to confirm the infection is gone.

Disconnect from the internet during the scan

Unplug your ethernet cable or turn off Wi-Fi before you start scanning. A virus can use your internet connection to read additional malware, contact attackers, or spread itself to other devices on your network. Staying offline during the removal process prevents these things from happening while your computer is vulnerable.

If you need to read antivirus software, do that on a different computer first, save it to a USB drive, then transfer it to the infected machine offline. Once the scan is complete and threats are removed, you can reconnect to the internet safely.

What to do if antivirus software cannot remove the virus

Some viruses embed themselves so deeply in your operating system that no scanner can remove them without breaking Windows or macOS. If multiple scans find the virus but cannot delete it, or if your computer is so slow that scanning takes hours, reinstalling your operating system is often faster and more reliable than trying to clean it.

Before you reinstall, back up any files you need. Connect an external hard drive, copy your Documents, Pictures, Desktop, and Downloads folders to it, then disconnect the drive from the infected computer. Do not back up executable files (.exe, .app, .msi) or system folders — viruses hide in those. Once your files are safe, use Windows installation media or macOS Recovery to erase the drive and reinstall from scratch.

Signs your computer has a virus

Watch for unexpected behavior: programs launching on their own, browser toolbars or search engines changing without your action, constant pop-up windows, files disappearing or becoming corrupted, or your computer running much slower than usual. Your antivirus software may also alert you to threats in real time.

Some viruses are silent and do not show obvious symptoms. They may steal passwords, use your computer to attack other machines, or mine cryptocurrency in the background. This is why running a scan periodically — even if nothing seems wrong — is a good habit. Set a reminder to run a full scan once a month.

Prevent reinfection after removal

Change your passwords for email, banking, and other sensitive accounts from a different computer, because the virus may have captured your keystrokes. Enable two-factor authentication on important accounts so that even if a password is stolen, an attacker cannot log in without a second verification step.

Update Windows or macOS and all your software to the latest versions. Most viruses exploit security holes that patches have already closed. Turn on automatic updates so you do not have to remember to do this manually. Keep your antivirus software running in the background and set it to scan on a schedule — weekly or monthly depending on how much you use the computer.

Be cautious about what you read and where you read it from. Viruses often hide inside cracked software, pirated movies or music, fake browser extensions, and email attachments from people you do not know. Stick to official sources: the Microsoft Store for Windows software, the App Store for Mac software, and the official websites of programs you trust.

When to consider professional help

If you are not comfortable working in Safe Mode, downloading software to a USB drive, or reinstalling your operating system, a local computer repair shop can do this work for you. Expect to pay between $100 and $300 for virus removal, depending on how infected your computer is and how long the repair takes. Some shops charge by the hour; others charge a flat fee.

Before you hand over your computer, ask the shop what they will do, how long it will take, and what it will cost. Ask whether they will back up your files before they start. Reputable shops will answer these questions clearly and give you a written estimate.

Frequently Asked Questions

Can I remove a virus without restarting my computer?

You can run a scan without restarting, but restarting into Safe Mode first makes removal much more likely to work. Viruses load during startup and can block antivirus software from deleting them while the system is running normally. Safe Mode prevents the virus from loading in the first place.

Is it safe to use my computer while a scan is running?

No. Close all other programs and let the scan run uninterrupted. Using your computer while scanning slows the process and can cause the antivirus software to miss infected files. A full scan can take one to three hours depending on how much data you have.

What if I see a pop-up saying my computer has a virus?

Do not click on it. These pop-ups are usually scareware — fake warnings designed to trick you into downloading malware or paying for fake removal software. Close the pop-up by pressing Alt + F4 or clicking the X button, then run a real scan with Windows Defender or Malwarebytes.

Can I catch a virus from visiting a website?

Yes, but it is rare on modern browsers and operating systems. Websites can try to exploit security holes to install malware, but Windows and macOS patches close most of these holes quickly. Keeping your operating system and browser updated is your best protection.

Do I need antivirus software if I have Windows Defender?

Windows Defender is sufficient for most users. It catches common viruses and malware without slowing your computer down. You only need additional antivirus software if you read a lot of files from untrusted sources or want extra layers of protection.