(A) Spyware is a term used for programs that contact servers on the Internet and don't tell you. Some of these actually watch your surfing habits or reveal details about your computer hardware and software. Often these programs disguise themselves as useful utilities to do things like accelerate your downloads or change your cursor. A list of spyware can be found here

(A) Personal firewall software can often block most spyware from contacting the outside world. In addition, there is a program called Ad Aware that can remove or disable spyware.