How to Scan for Malware in Windows 10

This guide walks you through the built-in and free methods to scan your Windows 10 PC for malware, including viruses, spyware, and other threats. You’ll learn how to run both quick and full scans using Windows Security, plus how to use Microsoft Defender Offline for stubborn infections. No third-party software is required.

What You’ll Need

• A Windows 10 PC with at least 1 GB of free disk space for the scan to work properly.
• Administrator access (you’ll need it to change scan settings and run offline scans).
• An internet connection for definition updates (recommended, but not strictly required).

Step-by-Step

1. Open Windows Security. Click the Start button, type “Windows Security,” and press Enter. You can also open it from the notification area (shield icon) or via Settings > Update & Security > Windows Security.
2. Check for updates first. In Windows Security, click “Virus & threat protection.” Under “Virus & threat protection updates,” click “Check for updates.” This ensures your malware definitions are current, which is critical for detecting the latest threats.
3. Run a Quick scan. On the same screen, click “Quick scan.” This scans common infection locations (like startup folders and running processes) and usually takes a few minutes. It’s a good first step if you suspect something but want to move fast.
4. Run a Full scan if needed. If the Quick scan finds nothing but you still have symptoms (pop-ups, slow performance, weird behavior), click “Scan options” (under the Quick scan button). Select “Full scan” and click “Scan now.” This checks all files and running programs on your hard drive. It can take an hour or more, so plan accordingly.
5. Review the results. After the scan finishes, you’ll see a list of threats. If any are found, Windows will either remove them automatically or ask you to take action. Click “Start actions” to apply recommended remediation.
6. Run Microsoft Defender Offline for stubborn malware. If the Full scan doesn’t clear the infection, or if malware prevents Windows from starting properly, use the offline scan. In Windows Security, go to “Virus & threat protection” > “Scan options” and select “Microsoft Defender Offline scan.” Click “Scan now.” Your PC will restart and boot into a special environment that runs a deep scan before Windows loads. This can remove rootkits and other persistent threats.
7. Check the protection history. After any scan, go to “Virus & threat protection” > “Protection history” to see detailed results, including quarantined items. You can restore a false positive if you’re sure it’s safe.

Common Mistakes

• Skipping definition updates. Scanning with outdated definitions is like looking for a new strain of flu with an old vaccine. Always update before scanning.
• Only doing a Quick scan. Quick scans miss many threats, especially those hidden in less common locations. If you have any reason to suspect malware, run a Full scan.
• Ignoring the results. If Windows finds a threat and you click “Allow” or “Restore” without thinking, you could re-infect your system. Only restore items you are 100% certain are safe.
• Running multiple antivirus programs. Having more than one real-time antivirus active can cause conflicts, slow your PC, and even prevent detection. Stick with Windows Security or one reputable third-party tool.
• Assuming a clean scan means you’re safe. No scanner is perfect. If you still have symptoms, consider other causes (e.g., hardware issues) or try a different scanning tool.

Tips

• Schedule regular scans. In Windows Security, go to “Virus & threat protection” > “Manage settings” > “Scheduled scan.” You can set a weekly Full scan at a time when your PC is on but you’re not using it.
• Use cloud-delivered protection. In the same settings, turn on “Cloud-delivered protection” and “Automatic sample submission.” This helps Microsoft catch new threats faster.
• Keep Windows updated. Many malware infections exploit vulnerabilities that are patched in Windows Update. Regularly check for updates to stay protected.
• Be cautious with email attachments and downloads. The best scan is the one you never need. Don’t open unexpected attachments or download from untrusted sites.
• If you use a third-party antivirus, check its own scan options. Most have similar quick/full/offline modes. The steps are analogous.

Troubleshooting

• Windows Security won’t open or shows an error. Try restarting your PC. If that fails, run the Windows Update troubleshooter (Settings > Update & Security > Troubleshoot > Additional troubleshooters). You can also reset Windows Security via Settings > Apps > Apps & features > Windows Security > Advanced options > Reset.
• Scan fails to complete or freezes. Close other programs and disable any third-party antivirus temporarily. If the scan still freezes, run a disk check (chkdsk /f in an elevated Command Prompt) to rule out disk errors, then try again.
• Malware is blocking Windows Security. Some malware disables security tools. Try booting into Safe Mode (Shift + Restart > Troubleshoot > Advanced options > Startup Settings > Restart > press 4) and then run the scan. Alternatively, use the Microsoft Defender Offline scan, which runs before Windows fully loads.
• Threat is found but can’t be removed. Try the offline scan. If that fails, quarantine the item manually via Protection history. You can also search Microsoft’s support site for the specific threat name for removal instructions.
• False positives. If you’re sure a file is safe (e.g., a cracked game or a niche utility), you can add it to exclusions in Windows Security (Virus & threat protection > Manage settings > Exclusions). But only do this for files you trust completely.

Frequently Asked Questions

Is Windows Security enough to protect my PC?

Yes, for most home users. Windows Security (formerly Windows Defender) provides real-time protection, cloud-delivered detection, and regular updates. It consistently scores well in independent tests. Just keep it on and updated.

How often should I run a full scan?

Once a week is a good cadence for most users. If you download a lot of files or visit risky sites, you might do it more often. The Quick scan can be run daily if you’re concerned.

What does “Microsoft Defender Offline” do?

It creates a bootable environment that runs a scan before Windows starts. This can detect and remove malware that hides deep in the system, such as rootkits, which normal scans might miss.

Can I use Windows Security alongside another antivirus?

You can, but Windows Security will automatically turn off its real-time protection if another antivirus is active. Running both at the same time can cause conflicts. It’s best to uninstall the third-party one or disable its real-time protection.

What should I do if my PC is infected and I can’t run any scans?

Try booting into Safe Mode with Networking (Shift + Restart > Troubleshoot > Advanced options > Startup Settings > Restart > press 5). Then update Windows Security and run a scan. If that fails, use the offline scan or create a Windows 10 installation USB and use the “Repair your computer” option to run a scan from the recovery environment.

Will a scan remove all types of malware?

No scanner catches everything. Some advanced threats (like certain fileless malware) are hard to detect. If you suspect a serious infection and scans come up clean, consider using a second-opinion scanner like Malwarebytes (free version) or resetting Windows.

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