10 Warning Signs Your Computer Has a Virus

The classic warning signs

1. Sudden, dramatic slowdowns

PC was fine last week and now crawls? Cryptominers and botnets burn your CPU in the background. Check Task Manager for unknown processes eating 90%+ CPU.

2. Pop-ups everywhere — even with no browser open

Adware infections push fake "virus warnings" and offers. Never click them, and never call the phone numbers shown — that's a tech-support scam.

3. Your browser homepage or search engine changed

Browser hijackers redirect your searches to ad-filled clones of Google/Bing. Resetting the browser usually fixes it (see our malware removal guide).

4. New toolbars, extensions or programs you didn't install

Check Apps → Installed apps sorted by install date, and your browser extensions list. Anything unfamiliar? Remove it.

5. Your antivirus is disabled and won't turn back on

Many infections first kill your protection. If Windows Security won't start or update, you're likely infected.

6. Files are encrypted or renamed (ransomware!)

Files open as garbage or have new extensions like .locked, .enc. Disconnect immediately and see the ransomware advice in our malware guide.

7. Friends receive spam "from you"

Your email or social accounts sending spam means either a stolen password or a PC infection. Change passwords from a clean device and enable 2FA.

8. High network activity when idle

Open Task Manager → Performance → see network traffic while you're doing nothing? Your PC may be part of a botnet. Disconnect and scan.

9. Programs open, close, or install by themselves

Remote-access trojans (RATs) let attackers control your PC. Disconnect from the internet and scan with a second-opinion tool immediately.

10. Passwords stop working

Can't log into accounts you know the password for? That account was likely stolen and changed. Start recovery immediately and secure other accounts with 2FA.

What to do if you spot these signs

Follow our complete malware removal guide, or let our technicians clean it remotely. Book malware removal.