The Seattle Times: Someone's watching you: Spyware likely hitching ride on your computer: "Computer viruses are rampant and spam is epidemic. But the fastest-growing Internet malady is spyware, and chances are your computer is infected.
Spyware is software that secretly forwards information about your online activities to a company or person without your knowledge or permission. In most cases, it is used to display advertising and is relatively benign.
As spyware programs accumulate, however, they can bog down your machine and its Internet connection. The most virulent forms can steal personal information.
Some experts say that up to 90 percent of computers online contain spyware. The situation is bad enough that Congress is considering a law banning such software practices. Internet service providers such as EarthLink have begun offering subscribers free spyware scans and removals.
In the first three months of EarthLink's offer, scans of more than 1 million hard drives found an average 28 spyware installations per PC. "