Unknowingly, some companies find themselves on adware

Well-known companies are advertising — sometimes inadvertently — through software often secretly installed on computers, according to a new report by a technology advocacy organization.

Ads from companies including Netflix, which rents DVDs by mail, and eHarmony, an online dating service, have popped up on PCs via advertising software, according to a report by the Center for Democracy & Technology, which pushes for free expression and privacy online. The center said the ad placement can occur without the companies’ knowledge.

Advertising software, or adware, launches ads, often in pop-up windows. It can be surreptitiously installed when users visit unscrupulous Web sites, a method called drive-by downloads, which exploit vulnerabilities in computer security. Adware also is installed, sometimes without consent, when users download free software.

Even companies that say they shun these ads may see them appear via adware because so many intermediaries are involved in placing online ads, said Ari Schwarz, deputy director of the center.

Schwarz said companies use advertising agencies, which work with advertising networks that place ads throughout the Internet. Those networks may work with other advertising networks, who subcontract to other networks, creating a long chain with as many as eight middlemen, Schwarz said.

Eventually, one of the advertising networks may turn to makers of adware, sometimes without the knowledge of the advertiser high up on the chain, Schwarz said.

Netflix has an in-house lab to ensure its advertising networks comply with the company’s “very strong and enforced policy of forbidding adware and spyware,” said Steve Swasey, spokesman for Netflix, based in Los Gatos, Calif.

Still, it’s difficult to completely eliminate the practice, he said. “It’s not like this is a billboard on Highway 680 that you drive by every day,” Swasey said. “It’s placed there by somebody doing it without your permission.”

It’s also harder for Netflix to track adware-related ads because of the volume of its advertising, Swasey said.