The pop-up claims a real antivirus scan found threats. But legitimate antivirus software cannot scan another website’s content or your device’s file system from inside a browser window.

Your heart races. Do you click “OK”? Do you call the number?

That alarming pop-up is almost certainly a scam. Here’s how to recognize it, why it’s dangerous, and exactly what to do if you see one. They are scareware — fake security alerts designed to trick you into taking action. Scammers use fear and urgency to bypass your logical thinking.

You’re browsing a website, looking for a recipe or checking sports scores. Suddenly, your phone or computer vibrates. A flashing red box appears: or “WINDOWS DETECTED MALWARE – CALL SUPPORT IMMEDIATELY.”