Not all of the programs that promise protection against viruses and other nasties have your best interests at heart. Some of them are actually Trojan horses – programs that pretend to be useful but actually do harm in the end. Others simply ape the real security software and try to scare you into paying money to clean up problems that don't really exist. For that reason they're often called scareware (and they’re also known as rogue software).
The existence of scareware is the computer using public’s fault, sadly. If absolutely nobody registered these programs the bad guys wouldn't be able to keep going – they'd find some other more lucrative scam to run. However, there are enough folks forking out £50 or so to register these fraud programs to keep the crooks in business.
These rogue programs may copy user interface elements from real programs; the multi-colour Windows security shield is especially popular. They often use names that sound similar to the real programs that you've heard of, too.
How can you avoid getting scammed? If you’re surfing the web and a warning suddenly pops up from an unheard of company/program, telling you that your PC is infected with multiple viruses – close the page immediately and don’t go clicking on any “scan” or “install” buttons.
If a security program that you never installed appears in the midst of your OS usage with a dire warning, then you’ve been scammed and have rogue software on board. If it's really, really hard to close the program – that’s another unsurprising piece of bad news. The biggest giveaway is often their incredibly fast virus scanning process. Since there's no real scanning going on the programmers can make it as fast as they want.
Before you consider paying money for any security utility, you should check the name of the program with a trusted source – say, Microsoft’s list of security software providers, or AVTest’s comprehensive list of tested suites. If the company’s name is on these lists, then fair enough – but check the name very carefully. As we’ve already noted, some scammers will call their product something very similar to a real security firm’s name in order to fool you.
Also note that scareware has progressed to cold calling on landlines, these days. If you get a phone call out of the blue from a “security firm” telling you that they’ve detected a virus on your Windows computer, again, these are simple scare tactics to get you to stump up for a rogue piece of software. Tell them you’re confused because your computer is a Mac running OS X, and you’ll hear the click of them hanging up, guaranteed.