How to run a malware scan

If you think a computer picked up a virus or other malware (harmful software), a scan is the safest first check. You will learn to run a quick, full and offline scan in Windows Security, and what a Mac already does for you.

What you need

• Windows 11 or Windows 10 for the steps below. Mac steps are in a separate section.
• A few minutes for a quick scan. A full scan can take much longer, so start it when you do not need the PC.
• Your files saved. The offline scan restarts the PC.

Windows Security is Microsoft's free security app that comes with Windows. If you installed security software from another well-known maker, use that program's scan instead, and keep only one active security program at a time.

Run a scan in Windows

Quick scan

1. Select Start, type Windows Security, and open the app.
2. Select Virus & threat protection. In Windows 11 you can also open Settings then Privacy & security then Windows Security. In Windows 10 the route is Settings then Update & Security then Windows Security.
3. Under Current threats, select Quick scan.
4. Wait for it to finish. The page shows when the scan ran, how long it took and how many files it checked. If it finds nothing, it says there are no current threats.

Full scan

1. In Virus & threat protection, under Current threats, select Scan options.
2. Select Full scan, then select Scan now. This checks every file and program on the device.
3. Leave the PC plugged in and let it run. You can keep using the computer, but it may feel slower.

Microsoft Defender Antivirus (offline scan)

Some malware hides while Windows is running. The offline scan restarts the PC and scans before Windows loads. It can help when malware is hard to remove or keeps coming back.

1. Save and close your open files.
2. In Scan options, select Microsoft Defender Antivirus (offline scan), then select Scan now.
3. Confirm. The PC restarts, scans, and restarts again by itself when finished.

See and handle the results

1. Open Windows Security and select Protection history.
2. Select an item to see what was found and what Windows did with it. Choose the offered action to remove or quarantine (isolate) a threat.
3. If Windows Security lists something under Allowed threats that you do not recognize, select it and choose Don't allow.

On a Mac

macOS has built-in malware protection called XProtect. Apple says it checks for known malware when an app is first opened, when an app has changed, and when its signatures are updated. Apple updates it automatically, independent of system updates, and by default a Mac checks for updates daily. Apple's security guide does not describe a button for starting a manual scan.

That means a Mac does not need a scan button as much as it needs good habits:

1. Install system updates. Open System Settings then General then Software Update (macOS Ventura and later; earlier: System Preferences > Software Update).
2. Open the Finder, select Applications, and move any program you do not remember installing to the Trash.
3. Check your browser for extensions you did not add, and remove them.
4. If you installed a security program from a well-known maker, open it and run its scan.

If something goes wrong

• If a scan will not start or the app says protection is off, restart the PC and try again. If you use security software from another maker, Windows Security may show that program as the active one.
• If the scan keeps finding the same threat, run the offline scan, then see safe downloads and fake driver sites to find how it got in.
• If someone else controlled your device, read what to do if you gave someone remote access.
• If a fake alert led you here, see fake virus pop-up: what to do.

Frequently asked questions