Pamela Fusco, an information security manager at an East Coast financial services company, said her team deals with spyware infections every day. The worst incident was spyware that began replicating so quickly that "in 20 seconds it nearly took down our Microsoft Exchange system," she said.

That is despite a comprehensive program Fusco set up for dealing with spyware, including antispyware technology from McAfee Inc. and SPI Dynamics Inc., constant PC audits, a global alert system, restrictions on the use of PCs for employees who don't need full access, and education programs involving live demonstrations or Web video. Another tactic enterprises should adopt includes closely monitoring their Domain Name System logs, said Kaminsky.

And Drew Maness, senior security strategist at The Walt Disney Co., suggested that IT help desk workers be trained to diagnose PCs that are running abnormally slow as possible hosts for spyware.

At Houston-based Continental Airlines Inc., spyware makes up 80 percent of the malware afflicting the airline's computers, according to Andre Gold, the company's chief information security officer. His team routinely deals with PCs that have been crippled by spyware by wiping the hard drive and reinstalling the complete operating system and software.

Asked how often his security team runs into particularly nasty spyware such as keyloggers that capture users' keystrokes -- including passwords and usernames -- Gold said, "I can't imagine a company that doesn't see it."