The spyware industry has amassed $2 billion from installing unwanted software on computers.
The State of Spyware Report, from anti-spyware company Webroot, reveals that pop-ups, hijacking home pages, redirecting searches, and using host file and DNS poisoning could make for over one-fifth of all online advertising revenue.
According to Webroot, businesses are particularly at risk.
"Attacks on financial institutions are just one example of the devastating damage spyware can inflict in a corporate environment," said Richard Stiennon, vice president of threat research at Webroot.
"Our research shows that some form of spyware, adware or potentially unwanted software can be found on 87 percent of corporate PCs. This figure is disconcerting from a security perspective and also from an IT support perspective, as spyware can often slow down the performance of an entire network," Stiennon added.
In the first quarter of 2005, 88 percent of computers had some form of spyware installed, the uses of which range from reporting sites visited for market research purposes, advertising and malicious collation of information.
Last week SC reported New York State Attorney General Eliot Spitzer filed suit against an internet marketing firm, alleging that it secretly installed spyware and adware on consumers' computers.