Motivated by the lure of profits from the sale of stolen confidential information, cyber criminals today are shifting to the Web as their chosen attack vector, which provides an ideal environment for cyber crime. Many Web threats can be deployed unbeknownst to the user, requiring no additional action than merely opening a Web page. Large numbers of users, an assortment of technologies, and a complex network structure provide criminals with the targets, exploitable weaknesses, and anonymity required for largescale fraud.