Guide
9 signs your laptop has a virus, and what to do
Most infections don't announce themselves with a skull on the screen. They show up as small, odd changes. Here are the signs worth taking seriously, and the safe order of what to do.
The signs
1. Pop-ups that appear even when your browser is closed
Adverts or "your PC is infected" warnings outside the browser usually mean adware or a scam app is installed.
2. Your browser homepage or search engine changed by itself
A classic sign of a browser hijacker, often installed alongside "free" software.
3. New toolbars, extensions or apps you didn't install
Check Settings → Apps and your browser's extensions page for anything unfamiliar.
4. Your anti-virus was switched off
Malware often tries to disable protection. If Windows Security shows real-time protection off and you didn't do it, treat it as serious.
5. Friends receive strange messages or emails from you
Your email or social accounts may be compromised, sometimes by a password stealer on your laptop.
6. The fan runs flat out when you're doing nothing
Hidden crypto-mining or other background malware can keep the processor busy. Check Task Manager for unfamiliar processes using lots of CPU.
7. Files you can't open, with strange extensions
Renamed, unreadable files plus a ransom note mean ransomware. Disconnect from the network immediately (see below).
8. Unexpected password-reset emails or banking alerts
Someone may be trying to use passwords stolen from your device.
9. Settings you can't change
Blocked access to Windows Security, Task Manager or Settings is a strong warning sign.
What to do, in this order
- If you see a ransom note, disconnect from Wi-Fi and unplug network cables straight away, and unplug any backup drives. Don't pay; get help.
- Don't log in to banking or enter passwords on that laptop until it's clean.
- Update and scan. In Windows Security, check for protection updates, then run a Full scan.
- Run an offline scan if anything was found or the signs continue: Windows Security → Virus & threat protection → Scan options → Microsoft Defender Offline scan. The laptop restarts and scans before Windows loads.
- Remove unfamiliar apps and browser extensions, and reset your browser settings.
- Change your passwords from a different, clean device, starting with email and banking, and turn on multi-factor authentication.
- Check your bank statements and tell your bank if anything looks wrong.
Our step-by-step guide to removing a virus from Windows goes into more detail.
Prevent the next one
Keep real-time protection on, install Windows updates, download software only from the publisher's own site or the Microsoft Store, and use a standard account day to day. CitadelLite Free Anti-Virus keeps an eye on all of this for you.
Frequently asked questions
Can a laptop have a virus without any signs?
Yes. Some malware, such as password stealers, is designed to stay quiet. That's why keeping real-time protection on and running regular scans matters even when everything seems fine.
Is a slow laptop always a virus?
No. Slowness is far more often a nearly full disk, too many start-up apps, an old hard drive or a pending update. Check those first, but run a scan to be sure.
Should I pay someone who calls to say my computer has a virus?
No. Microsoft and banks do not phone you about viruses on your computer. Hang up, never give remote access, and never pay.
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