Describes spyware, discusses how it gets on a computer. Explains how spyware can be useful for parents, employers, and libraries. Discusses how spyware is more often used for others' gain or for surveillance without notification, how it can go undetected, and how libraries can help keep computers and patrons protected from remote installation of spyware. Lists Web sites that offer information and software for cleaning spyware from the computer. (AEF)