One of the most persistent myths in tech support is that you need to buy antivirus software to be safe. You don't. Windows 10 and Windows 11 both include Windows Security (powered by Microsoft Defender), which independent testing labs consistently rate as one of the best antivirus products available — and it costs nothing.

Step 1: Open Windows Security

Click the Start menu and type Windows Security, then press Enter. You can also find it by clicking the shield icon in the system tray at the bottom-right of your screen.

Step 2: Go to Virus & Threat Protection

Click Virus & threat protection on the left. You'll see your current protection status. If it says No action needed, your real-time protection is active.

Step 3: Run a Full Scan

  1. Click Scan options (below the Quick scan button).
  2. Select Full scan.
  3. Click Scan now.

A full scan checks every file on your computer. It can take 30 minutes to a couple of hours depending on how much is stored on your machine. You can keep using your computer while it runs, though it may be a little slower.

Step 4: Review and Act on Results

When the scan finishes, Windows Security will show you what it found. For each threat you'll see options to Remove, Quarantine, or Allow. In almost every case, choose Remove or Quarantine. Only use Allow if you're certain something is a false positive — a legitimate file incorrectly flagged.

Step 5: Run an Offline Scan for Stubborn Threats

Some malware hides from regular scans. For these, use the Microsoft Defender Offline scan:

  1. In Scan options, select Microsoft Defender Antivirus (offline scan).
  2. Click Scan now.
  3. Your computer will restart and scan before Windows fully loads, making it much harder for malware to hide.
Watch out for fake security software. If a pop-up or ad is urging you to download a "cleaner" or "antivirus" tool, that program is often the malware itself. Stick with Windows Security — it's already on your computer and it's free.

Keep Real-Time Protection On

Real-time protection catches threats the moment they appear. Make sure it's enabled by going to Virus & threat protection > Virus & threat protection settings and checking that Real-time protection is toggled on.

If Windows Security won't turn on, see our guide on fixing Microsoft Defender. Still need help? Ask us.