Start with the built-in scanner your operating system provides

Windows and Mac both include malware scanning tools you already own. On Windows 10 and 11, open Windows Security (search for it in the taskbar), click Virus & threat protection, then click Scan options. Choose Full scan — this takes longer than a quick scan but checks every file on your drive. The scan can take an hour or more depending on how much data you have. Let it finish without interrupting.

On Mac, open System Preferences, go to Security & Privacy, then the General tab. Mac runs automatic malware checks in the background, but you can also run a manual scan using the built-in XProtect tool — though Apple does not give you a visible button for this. The easiest route on Mac is to restart your computer while holding Command + R to enter Recovery Mode, then run Disk Utility's security scan.

These built-in tools catch the most common threats. They are free and do not slow your computer down the way some third-party antivirus software does. If the scan finds nothing, you may still want to run a second opinion scan using a different tool, because no single scanner catches everything.

Key Takeaways

  • Windows Security and Mac's built-in tools are your first line of defense and do not cost extra.
  • A full scan checks every file on your computer and can take an hour or longer to complete.
  • Running a second scan with a different tool catches threats the first scan might have missed.
  • Malwarebytes and Kaspersky are reputable free scanners that work alongside your main antivirus tool.
  • If a scan finds malware, restart in Safe Mode before removing it to prevent the malware from protecting itself.

Use a second-opinion scanner for threats the first scan missed

Malwarebytes and Kaspersky Rescue Disk are two widely used tools that find malware your main antivirus might overlook. read Malwarebytes from malwarebytes.com — the free version scans and removes threats without paying. Install it, open the program, click Scan, and let it run. This usually takes 15 to 30 minutes.

Kaspersky Rescue Disk is more thorough but also more involved. You read an ISO file from kaspersky.com, burn it to a USB drive using a tool like Rufus (on Windows) or Disk Utility (on Mac), then restart your computer and boot from the USB. This scans your computer before Windows or Mac even loads, so malware cannot hide or protect itself. Use this method if Malwarebytes finds something serious or if you suspect a rootkit — malware that burrows deep into your system.

Do not install both Malwarebytes and a paid antivirus program at the same time; they can conflict. Malwarebytes is designed to work alongside Windows Security or Mac's built-in protection, not replace it.

Restart in Safe Mode before removing malware

If a scan finds malware, restart your computer in Safe Mode before trying to remove it. Safe Mode loads only the bare minimum of programs and drivers, which prevents malware from running and protecting itself while you delete it.

On Windows 10 and 11, hold the Shift key and click the power button, then select Restart. When the blue screen appears, click Troubleshoot, then Advanced options, then Startup Settings, then Restart. When the list appears, press 4 or F4 to enter Safe Mode. On Mac, restart and hold Command + S when ready after you hear the startup sound, then type fsck -fy and press Enter when prompted.

Once in Safe Mode, run your malware scanner again. The malware is less able to resist removal when it cannot run in the background. After removal, restart normally and run the scan one more time to confirm the threat is gone.

Check your browser for unwanted extensions and homepage changes

Malware often installs fake browser extensions or changes your homepage and search engine without permission. Open your browser — Chrome, Firefox, Edge, or Safari — and look for unfamiliar add-ons.

In Chrome, click the three-dot menu, go to Extensions, and review the list. Anything you do not recognize should be removed by clicking the trash icon. In Firefox, click the menu button, select Add-ons and themes, then Extensions, and remove anything suspicious. In Edge, click the three-dot menu, select Extensions, and delete unfamiliar ones. On Safari, click Safari in the menu bar, select Preferences, go to the Extensions tab, and remove anything you did not install yourself.

Next, check your homepage and search engine. In Chrome, click the menu, go to Settings, then On startup, and make sure it opens to a page you chose. Check Search engine in the same menu. Do the same in Firefox, Edge, and Safari. If your browser keeps resetting these settings after you change them, malware is still running — go back and run another full scan.

Review startup programs and scheduled tasks

Malware often sets itself to run automatically when your computer starts. On Windows, 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. Do not delete it — disabling is safer in case you were wrong about what it is.

You can also check the Startup folder directly. Press Windows key + R, type shell:startup, and press Enter. Any files in this folder run when Windows starts. Delete anything you do not recognize.

On Mac, go to System Preferences, click General, then Login Items. Remove any programs that should not be there. Mac also has a Allow in the Login Window section — check that too.

Look for signs of malware between scans

Even if a scan finds nothing, watch for warning signs. If your computer is suddenly slow, your fan runs constantly, your browser shows pop-ups you cannot close, or you see unfamiliar programs in your Applications folder, malware may be present but hidden.

Check your network activity using a tool like Wireshark (free, wireshark.org) to see what data your computer is sending. Malware often phones home to a server to steal information or receive commands. If you see traffic to unfamiliar IP addresses, that is a red flag.

If you suspect malware but cannot find it, consider backing up your important files to an external drive, then doing a clean Windows or Mac reinstall. This is the most reliable way to remove deeply hidden malware, though it takes several hours and erases everything on your drive.

Keep your system updated to prevent future infections

Most malware enters through security holes in Windows, Mac, or your browser. Turn on automatic updates so patches arrive as soon as they are released. On Windows, go to Settings, click Update & Security, and make sure Automatic is selected. On Mac, go to System Preferences, click Software Update, and check Automatically keep my Mac up to date.

Update your browser and browser extensions too. Chrome and Firefox update automatically, but check Safari and Edge manually. Also update any other software you use regularly — Adobe Reader, Java, and older programs are common targets.

Beyond updates, avoid downloading files from untrusted websites, do not open email attachments from people you do not know, and be cautious with USB drives from others. These are the most common ways malware spreads to home computers.

Frequently Asked Questions

How often should I scan my computer for malware?

Run a full scan at least once a month if you browse the web regularly. If you visit risky sites, read files often, or notice your computer acting strangely, scan weekly. Most people do not need to scan more than that if they keep their system updated and use a password manager to avoid phishing.

Is free antivirus software as good as paid versions?

Windows Security and Malwarebytes free catch the vast majority of common threats. Paid antivirus software adds features like real-time scanning and firewall management, but they also slow your computer down more. For most home users, the free tools are enough if you also keep your system updated and practice safe browsing habits.

What should I do if malware keeps coming back after I remove it?

If removal does not stick, the malware may have infected your browser, your startup programs, or your system files. Run a scan in Safe Mode, check your browser extensions and startup programs again, and consider using Kaspersky Rescue Disk to scan before Windows loads. If it still returns, a clean reinstall of Windows or Mac is the most reliable solution.

Can malware hide from antivirus scans?

Yes. Rootkits and some advanced malware can hide from standard scans by running at a level below the operating system. This is why running a scan in Safe Mode or using a bootable scanner like Kaspersky Rescue Disk helps — they scan before malware has a chance to hide itself.

Do I need both Windows Security and a third-party antivirus?

No. Windows Security is sufficient for most people. Adding a paid antivirus program on top of it can actually cause problems because they conflict with each other. Use Malwarebytes as a second-opinion scanner instead — it is designed to work alongside Windows Security without conflict.