Check the article link below for detailed analysis of a nasty form of malware
Chalk up another success for what's generally known as the "fake antivirus" scam. Federal investigators and security experts estimate that its various iterations have extracted at least $1 billion from victims in the past several years, and it has become the most visible manifestation of an overall rise in malicious software, or "malware," distributed online (see charts below). The damage goes beyond the theft of cash: even if you don't pull out your wallet, sometimes merely clicking on the bogus come-ons can deliver other forms of malware that may steal your passwords or conscript your computer into a remotely controlled gang called a botnet. Because it generally relies on fooling people into voluntarily installing malware—a strategy called a social-engineering attack—it can wind up infecting even well-maintained machines, both PCs and Macs. "As a human-level act of deception, it is just classically beautiful," says David Clark, a research scientist at MIT's Computer Science and Artificial Intelligence Laboratory, who was the Internet's chief protocol architect in the 1980s.