The Internet service provider worked with security company Webroot's software to scan consumer PCs, surveying more than 3 million systems between January and September. The study found 83 million instances of spyware, a sign of increasing bombardment by malicious software.
CNET.com has reviews of antivirus and filtering software that tackle spyware infections, and CNET Download.com's Spyware Center offers information--and free programs--to address the problem.
Spyware programs hide in PCs and secretly monitor user activity. Typically, spyware arrives bundled with freeware or shareware, or through e-mail or instant messages. The programs are difficult to remove and may cause computers to run slowly or even crash.
At times, they can even be dangerous because some pop-up programs can steal passwords. Last month, California's legislature passed an antispyware bill that bans unauthorized installation of spyware on unsuspecting computer users.
EarthLink distributes free copies of antispyware software such as its SpyAudit and Spyware Blocker and Webroot's Spy Sweeper to its customers.