At a panel discussion Wednesday during the Black Hat security conference in Las Vegas, speakers said that antispyware vendors are losing the fight against spyware creators, making more drastic measures necessary.

"It's not technically feasible to stop spyware," said Dan Kaminsky, an independent security consultant. "Think of the millions of PCs that have either been put away for good, sent away for service or replaced because of spyware infections. That is probably hundreds of millions or billions of dollars worth of damage. Yet no one has gone to jail; no one has been sued."

Recent statistics gathered by antispyware vendor Webroot Software Inc. point to spyware's continued growth. Between March and June, more than 100,000 new Web sites hosting spyware were discovered by Webroot. That's in addition to the 427,000 such sites discovered by Webroot since it began searching for them in January 2004 using a specially tuned search engine that Gerhard Eschelbeck, chief technology officer of Webroot, calls a "Google for spyware."

"Viruses are pretty easy to track -- you just stick out the sensor," Eschelbeck said. "Spyware is pretty hard to track down. You've got to actively hunt it down because it changes every day, every hour."

According to Webroot, 31 percent of all PCs -- including those that are business-owned -- have been infected with Trojan horses, which typically arrive disguised as something innocuous, such as a picture or document. An infected PC at an enterprise is host to an average of 1.3 Trojans, which Webroot considers the worst form of spyware -- although they can be more malicious than that.