AdSubtract of Braintree, Mass., is the latest example of a company offering such a service that blocks advertisements and unique computer identifiers, called cookies, that are used to track a consumer's habits online whether shopping or just surfing the Net.
Another program, presented by McAfee at the Demo2000 conference in Palm Springs, promises to protect users' privacy while at the same time allowing advertisements targeted to an individual's preferences.
Privacy advocates say demand for such blocking devices will rise as more people become aware of advertisers' profiling techniques.
"Undoubtedly people are becoming aware of a threat to their privacy," said Jason Catlett, founder of Junkbusters, a resource site for privacy protection measures. "Now companies are jumping on that awareness as a marketing opportunity."
AdSubtract's and McAfee's new programs join others in an emerging field that includes Junkbusters' free blocking device. WebWasher, a program from German company Siemens, is also a contender in this growing area.
But AdSubtract's new program, called AdSubtract SE, specifically targets ads and cookies assigned by online advertising giant DoubleClick, which has come under fire recently for its consumer profiling plans.
News of the new policy touched off a fury among privacy advocates. In early February, the Center for Democracy and Technology organized a protest against DoubleClick.
"Internet advertising is fueling the growth of the Internet by allowing sites to offer content and services free of charge," a DoubleClick representative said in an email. "Without ad support, only the elite would have access to the Internet."
Ed English, president of AdSubtract, said he specifically targeted DoubleClick because they are "the most aggressive about profiling."
AdSubtract's program comes with a theme that includes military sound effects. A gunshot rings out each time an advertisement is blocked. When the program discovers cookies, a cannon fires.
"Sometimes it's like you're in the middle of a battlefield," he said. "You can turn the sound off, but we put it there to demonstrate how stealthy advertisers can be."
McAfee's program focuses on allowing targeted advertisements to reach an individual without releasing personal information about the consumer, McAfee president Srivats Sampath said.
Someday, Sampath said, users will be able to choose which ads are preferable.
Catlett lauded the new program, calling it "a step in the right direction."
Others services that allow advertising but protect privacy include Enonymous.com, which claims to evaluate the privacy policies of more than 25,000 Web sites.
Catlett and other privacy advocates said blocking services will eventually play a role in forcing advertisers to conduct business responsibly.
"We caution people to think long and hard about giving up any personal information over the Internet," said Beth Givens, director of San Diego- based Privacy Rights Clearinghouse, a nonprofit consumer information and advocacy program.
"Profiling is only going to get richer and richer and there is no knowledge of how the information will be used down the line," Givens said.