Since the early days of the internet, web surfers have dealt with the annoyance of pop-up ads. Some pop-ups, however, do more than just annoy. Some serve a very specific function: to trick you into believing your computer is infected with malware and use that fear to sell you worthless “tech support” and software.

So imagine you are exploring the many wonders of the world wide web, when a window on your computer—seemingly legitimate—abruptly opens, freezes your computer, and tells you that your system is infected with viruses and malware. Fortunately for you (or so you think), the window provides you a phone number to call to avoid disaster. The representative on the line mentions that they are associated with Microsoft or Apple and proceeds to tell you that you are at risk of losing all of your work files and years of family pictures. But, for only $299.99, the representative can install software and assist in fixing your computer. Then comes the upsell. Before you know it, you have been signed up for hundreds of dollars’ worth of tech support and software you did not actually need. You’ve been scammed.