NebuAd Inc.

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.

Embarq Corp. has revealed more details about its exploration of a program that tracked Internet subscribers' Web-surfing habits for advertising purposes, telling Congress that it performed the test on 26,000 customers in a Kansas town.

Building on an earlier response to Rep. John Dingell, chairman of the House Energy and Commerce Committee, Embarq CEO Thomas Gerke wrote in a letter late Wednesday that his Overland Park, Kan.-based company chose Gardner, Kan., for its test because it was Embarq's smallest market and near qualified technicians.

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.

Microsoft Corp. and Google Inc. told lawmakers Wednesday that Congress should pass basic privacy legislation to protect information about consumers, such as the data being gathered about people's Web surfing habits in order to pinpoint Internet advertising.

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.