PCs infested with spyware

In a "spyware audit" of more than 1 million computers, Earthlink found more than 29.5 million examples of spyware installed-- an average of nearly 30 spyware programs installed per computer. BBC News reports: PCs 'infested' with spy programs

These are parasite programs sometimes come attached to software downloaded from the web.

The details are often included in the license agreement small print that most users click through without reading.

But sometimes they do not even need your permission to download, but just bury themselves on a hard drive as you browse the net.

With the exception of pop-up ads or a slower computer, people may not notice anything different when spyware programs are present, say experts.