Embarq Corp.

Angry online subscribers who had their Web surfing habits tracked in detail are suing a Silicon Valley startup that created the technology and six Internet service providers that briefly used it.

The 15 customers who filed the lawsuit in federal court here Monday demand more than $5 million in damages and are asking a judge to turn the case into a class action representing tens of thousands of Internet subscribers.

Congress has asked Embarq Corp. about its work with a company that tracks online subscribers' Web traffic for advertising purposes, part of growing concern about Internet privacy.

Overland Park, Kan.-based Embarq is the nation's fourth-largest traditional telephone company with 1.34 million high-speed Internet subscribers in 14 states. It has been linked in the past with NebuAd Inc., a company that works with Internet service providers to tailor targeted ads based on what Web sites a particular subscriber visits.

Although a large Internet service provider has backed away from technology that tracks subscribers' Web use in order to deliver personalized advertising, two other broadband companies said Wednesday they are still considering whether to deploy it.

Phone companies Embarq Corp. and CenturyTel Inc. have both completed trials of the same tracking system, from online advertising company NebuAd Inc., and are now considering whether to proceed.