PHILADELPHIA — The Justice Department is demanding internal files from dozens of Internet service providers and other technology firms as it seeks to defend a controversial Internet child-protection law.

The subpoenas are similar to one given to Google Inc., which waged a partly successful battle over the government's request for millions of pieces of information about search engine requests and Web site domains.

InformationWeek magazine unearthed subpoenas that show the government also demanded information from at least 34 other companies, including Internet service providers such as Comcast Corp. and Earthlink, security software firms and other technology companies.

The subpoenas, which the magazine obtained through Freedom of Information Act requests, show the Justice Department preparing for an October trial in Philadelphia over the 1996 Child Online Protection Act. It is not clear which companies are complying, and to what extent.

"That money could be spent so much more wisely on giving software away to parents that are having these problems," Dan Jude, president of Security Software Systems, said of the litigation costs.

The 12-person firm, which makes filtering software, spent more than 40 hours trying to comply with the subpoena, he said. The company refused to provide some information on proprietary grounds, fearing it could make its way into the court file.

"If that information gets out in the public, we've just lost our competitive edge," Jude said yesterday. The subpoena also sought information the company does not keep, such as customer satisfaction, he said.

Department of Justice spokesman Charles Miller did not immediately return a message yesterday afternoon.

The subpoenas also went out to companies including AT&T;, Cox Communications, Verizon and Symantec.

The U.S. Supreme Court has twice said the law — which would criminalize Internet material deemed "harmful to children" as defined by "contemporary community standards" — is likely to violate First Amendment protections and granted preliminary injunctions to keep the law from going into effect. (See 2002 ruling, Ashcroft v. ACLU and 2004 ruling, Ashcroft v. ACLU, II.)

Critics say that definition is so broad it would stifle free speech, and also note that pornographers and others could simply base their operations offshore, beyond the reach of U.S. authorities.

Online publishers who are challenging the law argue that filters are a less restrictive way to protect children. The publishers, which include sexual health sites, a gay newspaper and the online magazine Salon.com, are represented by the American Civil Liberties Union.

"Our overarching concern over what the government is doing (with the subpoenas) stems from the 'why,' — what is it they're actually trying to accomplish?" said David McGuire, a spokesman for the Center for Democracy and Technology in Washington. "It doesn't seem reasonable."