In fact, news.com states that almost one-third of computer users in the U.S. have been hit by a virus or hacker in the past two years. When I clean up malicious programs, clients are often surprised to learn they have inadvertently given permission to outsiders to use their computer, slowing it to a crawl, exhausting memory, and risking safety of your data.
Read more at www.news.com or search some of the Internet news sites like Cnet's excellent industry news at www.news.com, www.pcmag.com or www.eweek.com. Those most affected by this are using music download software and/or instant messaging services, which leave a back door open for people to tap into your computer.
Spyware is capable of tracking your Web browsing and reporting information to third-party companies who sell the information to others. Removing it can also be destructive to some components of Windows.
... From News.com: "Virginia Watson unwittingly authorized a company she'd never heard of to install software that would help turn her computer into part of a brand-new network.
The software, from Brilliant Digital Entertainment, came with the popular Kazaa file-swapping program. But the 65-year-old Massachusetts resident--who has a law degree--didn't read Kazaa's 2,644-word "terms of service" contract, which stated that Brilliant might tap the "unused computing power and storage space" of Watson's computer."
The man who owns Brilliant is quite clever. In fact the sentence structure in his license agreement has been analyzed for complexity, and found to be more complex than the U.S. tax code. And keep in mind the "free" software is targeted mostly to teenagers.
Prevention methods include vigorous use of anti-virus, firewall, AdAware and Spybot programs.