But with the exception of pop-up ads or slower operations, users may not notice anything happening when spyware programs are present, experts say. And the programs often apply a legal fig leaf by asking for consent to be installed as part of a lengthy EULA (End User License Agreement) that many users OK without reading.
In Congress, a bill to battle spyware sponsored by Sens. Barbara Boxer (D) of California, Ron Wyden (D) of Oregon, and Conrad Burns (R) of Montana recently joined one filed in the House last July by Rep. Mary Bono (R) of California. They aim to ensure that users know when programs are being installed on their computers, so that they can refuse them if they wish, and that spyware that is installed is just as easily removed. The Federal Trade Commission would enforce compliance.
The FTC has already announced that it is holding a spyware workshop in Washington on April 19 to gather information about the problem.
In addition, the Utah legislature has sent a bill regulating spyware to the governor for his signature. Iowa and California have also considered bills to prevent spyware.
"The Internet is a window on the world, but spyware allows virtual Peeping Toms to watch where you go and what you do on the Internet," Senator Wyden said in a statement about the Senate bill, called the Spyblock Act.
"The FTC is beginning to look at the extent to which these applications are unfair and deceptive, and we think that's a really good thing," Mr. Steffen said in phone interview. "We think a lot of these [spyware] programs already represent violations under existing fraud statutes or under other laws."
Although new legislation may have a role to play, Steffen says any solution must also include educating the public, and self-regulation within the industry.
"The spyware and adware stuff comes in from all over, and it's really as dangerous as a virus," says Roger Thompson, vice president for product development at PestPatrol in Carlisle, Pa., a maker of antispyware software.