If you've ever gotten a pop-up message warning that your PC is infected, it could very well be an advertisement for rogue software that can do a lot of harm and absolutely no good.
Symantec has just issued a report saying that the company has "detected over 250 distinct rogue security software programs." These scams try to convince users that their machine is infected and offer software for purchase that will take care of the problem. But instead of removing security threats, it can create them by installing malicious code that can allow criminals to take over the victim's computer. In addition, a user who provides a credit card number to buy the software is not only out the cost of the software but has just provided credit card information to thieves who can misuse it or sell it to other thieves.
The "security software" often has a legitimate sounding name and may even quotes what appears to be a review from a legitimate source.
In a podcast interview, Symantec Security vice president Vince Weafer warns users not to respond to security messages that they view as pop-ups or on websites, especially if they look like a hard-sell. Instead, rely on legitimate security software. If you have any doubts, Symnatec and other legitimate security companies offer free scanners that can tell you if you have any infections. Also, Microsoft now offers its free Security Essentials that can detect and fix many security threats.