Spyware can come from a variety of locations. Here are some examples on how it can be downloaded to your computer (Links within junk emails, clicking on suspicious pop-ups, file sharing programs, visiting websites that have been infected, downloading free utilities, games, converters, players, and toolbars).
These infections can do a lot of damage to your machine, as well as steal your personal information. Spyware can also spam your inbox with junk emails, slow down your connections, crash your PC, pollute your web browsers with pop-ups and toolbars.