Fake Virus Warning
A pop-up, browser tab, or full-screen alert appears claiming the computer is infected, often with urgent language, a countdown, fake system sounds, or a phone number to call.
Quick answer: A pop-up claiming your computer is infected and urging you to call a phone number or download software immediately is almost always a scam, not a real security alert — genuine antivirus software doesn't work this way. Don't call the number and don't download anything it suggests.
Likely causes
- A malicious or misleading advertisement on a website (this doesn't necessarily mean the computer is actually infected)
- A scareware program that's been installed and is generating fake alerts intentionally
- A phishing attempt designed to trick you into calling a fake support number or installing remote access software
What you can safely check yourself
- Don't call any phone number shown in the warning, and don't download or install anything it suggests
- Close the browser entirely (Task Manager if it won't close normally) rather than clicking anything within the warning itself
- Run a scan with Windows Security afterwards to check whether anything is actually present
If you've already called a number from one of these warnings and someone asked for remote access, payment, or gift cards, stop the call immediately and don't provide any of those — get the computer checked properly afterwards.
When it needs a proper look
If you interacted with the warning at all — called the number, allowed remote access, or downloaded something — get the computer checked properly rather than assuming it's fine.