What's up with those viruses?

So you're browsing the Internet, minding your own business, when all of a sudden there's a popup prompting you to "scan now" for security threats. You do so immediately because you're a conscientious library user. And in any case, who doesn't want to run a random scan once or twice a week? You expect to find no problems, but to your horror, that "trusty" antivirus app starts reporting several viruses and security threats. Even worse, the app declares that you have to purchase an upgrade in order to remove the viruses from the computer. This scenario represents a sure case of Internet fraud known as scareware. Scareware takes the form of very official looking software packages that hijack computers and fool users into relinquishing credit card information. If a library computer ever prompts you to scan for viruses, security threats, etc., please DO NOT do so. Don't even click the cancel or X button. Simply navigate away from the website through which you encountered the popup because it has been hijacked by malicious software. If the "scan" has already begun, please inform a member of the library staff.