Facebook users who added the "Secret Crush" application to their profile got a surprise recently when they found that instead of revealing who that secret someone might be, they received an invitation to visit a website and download adware files that would produce pop-up ads on their computers. The application, which spread by requiring each Facebook user who wanted to find out the name of their secret crush to convince five other Facebook friends to also add it, had over 50,000 users as of early January, according to IT security firm Sophos, which alerted its clients in a bulletin on January 4th.

If you're using Facebook or MySpace or another social networking site (or your children are), you need to use the same common sense caution when asked to add an application or share your personal information with any outside vendor or source. The appeal of these applications is great: they seem like simple, fun ways to interact with your friends, sharing photos or videos, playing games, chatting and so on. But despite attempts by Facebook to maintain some control over the quality and legitimacy of these applications, potentially malicious ones are inevitable. Be cautious; you can probably get along without knowing the name of your "Secret Crush," especially if the trade-off is annoying pop-up ads - or worse.