Spyware is a computer program that becomes installed on a user's PC without their knowledge, gathers personal and user-behaviour information concerning the user, and sends that information to a third party. Although there are differences depending on the kind of spyware, the capability of gathering personal information (such as e-mail addresses, phone numbers, and passwords), information stored on a PC, and information on browser usage is common in all kinds. The gathered information is chiefly used for marketing purposes.
