Popular Internet services that allow computer users to swap music and video clips also are an easy and free-flowing conduit for pornography, including images of minors, according to two congressional reports to be released today.

Teenagers -- who are among the heaviest users of sharing services -- might accidentally be exposed to pornographic files because they often have innocuous labels that users often seek, the reports say. And parents might not realize how much pornography is available on the services, according to the studies produced by the General Accounting Office and the House Committee on Government Reform.

"We need to alert parents to this problem and learn what they can do about it," said Rep. Thomas M. Davis III (R-Va.), who will chair hearings on the matter this morning. "Seemingly innocent searches for files containing images of popular cartoon characters, singers and actors produce thousands of graphic pornographic images including child pornography."

In one test, the GAO used the market-leading Kazaa sharing software to search for titles containing the names "Britney," "the Olsen twins" (Mary-Kate and Ashley) and "Pokemon." Of the total number of files that showed up, 56 percent included some form of pornography, with 8 percent involving minors.

When investigators used search terms specifically designed to yield pornography, 44 percent of results involved minors.

The reports raise a fresh controversy for these "peer-to-peer" networks, which have grown to attract hundreds of millions of users worldwide since Napster Inc. first burst on the scene in the late 1990s. And the issue is yet another indication of the growing tension computer users face in balancing the wonders of the Internet with its potential dangers.

Pornography has long been widely available on the Internet, through e-mail, chat rooms and Web sites offering graphic images and video. Internet service providers and software makers have tried to limit the chance of minors encountering porn by giving parents filtering tools that can block certain sites or limit the ability to surf the Web.

File-sharing software acts as an entertainment matchmaker, connecting computer users directly to each other so that the digital music and video files of one individual can be downloaded by another. Some file-sharing services also offer filtering options, but they are generally less effective and can be easily disabled, according to the congressional reports.

"Parents need to know that the file-sharing world is a lot more graphic than the Web," said Rep. Henry A. Waxman (D-Calif.), the top Democrat on the reform committee. "On the Web, you generally need a credit card to access hard-core adult videos, but on file-sharing programs, it's all free. And on the Web, you can rely on parental control software to filter out the worst stuff, but you can't with file-sharing programs."

So far, neither Davis nor Waxman are proposing legislation, opting simply to warn parents of what is available through file sharing.

But the concern serves to bolster the aims of the music and movie industries, which have long sought to drive the sharing services out of business, arguing that they violate copyrights by allowing people to acquire music and videos without paying for them.

"We've been keeping our eye on this ball for a long time because there's a lot going on in the peer-to-peer environment that people aren't aware of," said one industry executive. The entertainment industry has largely prevailed in the courts, winning rulings that led to Napster's closure, for example. But numerous services, such as Kazaa, Morpheus, LimeWire and Grokster, continue to flourish.

Kazaa software has been downloaded 200 million times, and the company that offers it estimates that 4 million consumers use it at any given time.

Overall, the recording industry estimates that 41 percent of music downloads are by children between the ages of 12 and 18.

Representatives of the file-sharing networks said yesterday that they recognize that some pornography is on their systems, many of which offer rudimentary filtering tools. But they view their role as no different from that of other technology providers.

"We have no more knowledge of what people do on our network than Microsoft has with people who use [the Web browser] Internet Explorer or AOL does when people get together in a chat room," said Philip S. Corwin, a Washington attorney and lobbyist for Sharman Networks, which owns Kazaa.

A company spokeswoman added that "all of us utterly abhor child pornography, and on the few occasions when we've been contacted by law enforcement . . . we have fully cooperated to the best of our ability."

Greg Bildson, chief technology officer for Lime Wire LLC, said his firm always seeks to improve its technology, but it faces many priorities.

"We're content agnostic," he said. "I can see this as being a concern to a parent, but there's no perfect solution. It's nice to put family filters on, and there's more work we can do, but it's hit or miss on whether it can work."

Fred von Lohmann, a staff attorney with digital rights group the Electronic Frontier Foundation who also represents Morpheus, said the country needs to recognize that technology can be used for good and bad.

"For concerned parents, the message is, you have to supervise what your children are doing online," he said. Regulations are not the answer, he added.