While spyware blooms, adware appears to be wilting. The average infected enterprise PC today is host to 2.8 instances of adware, down from 3.9 in the fall of 2005.

Not everyone agrees on the difference between relatively benign adware and more malignant spyware, which Kaminsky said is one reason it's been so difficult to fight the latter.

He said laws must be put in place that clearly set out guidelines for would-be adware distributors. For instance, laws could spell out that ads need to removable by users within 10 seconds with a simple right-click of the mouse lest they be deemed spyware. "As long as everything is gray, no one goes to jail," he said.

Fusco agreed that laws today are inadequate for stopping spyware at its sources. But Gold said another problem is the reluctance by companies infected by spyware to come forward and share information with government agencies.

"If I give you data, you could help me -- or you could prosecute me" for lack of due diligence, Gold said. "It's an absolute Catch-22."