Scareware
Also known as: fake virus alert, browser locker, fake tech support popup
Fake security warnings that try to panic you into calling a phone number, paying for useless software, or installing real malware.
Scareware is the umbrella term for fake virus alerts, system warnings, and tech support pop-ups. A common version: your browser locks, a loud siren plays, and a full-screen banner reads “Your computer is infected with 5 viruses. Call Microsoft Support immediately at 1-800-XXX-XXXX.” The pop-up is HTML, not a real system message — but to a non-technical user it looks identical to a real Windows error.
The goal of scareware is to get you to call a fraudulent support number where the scammer either sells you useless “premium antivirus” or asks you to install remote-access software so they can drain your accounts directly.
Real Windows and macOS errors never include a phone number, never play sirens, and never instruct you to call a specific company. If you see one, close the browser using Task Manager (Ctrl+Shift+Esc) or force-quit, then run a real antivirus scan.