Darknets: P2P by invite only

These are "darknets": exclusive peer-to-peer networks in which membership is based on circles of trust, whose activities are veiled from the general public. And though people who are adept at configuring servers and comfortable with File Transfer Protocol have used such systems for years, a spate of new online services aimed at everyday users is sure to draw new attention to under-the-radar file sharing.

Darknets, like their peer-to-peer predecessors Kazaa, Napster and Gnutella, allow users to browse and download digital files such as movies and music from other people's computers. But while Napster and its ilk have allowed unrestricted access to files on any of the millions of connected computers, darknets are more discriminating. In a darknet, users get access only through established relationships--and only when they have been invited to join. This selectivity promises greater privacy, regardless of whether the networks are used for sharing personal or pirated media.

File sharers may be enthusiastic about the possibilities such services provide, but there are questions as to whether any new service facilitating file swapping can avoid the legal scrutiny that has hampered open-access file-sharing systems.

Grouper, among the largest of the new services, hosts more than 100,000 private groups. Users can build their own darknets or request admission to thousands of publicly listed clubs whose members can browse through group folders, download files and communicate by instant messaging or group blogs.

A Bible group on Grouper, Deepthings, shares e-books and audio tapes. Needles and Pins offers sewing patterns. Skater Paradise posts skateboarding videos.

Grouper is currently a free service, and contextual ads in its group directory help generate revenue. Soon the company will include video ads and the option to buy photo prints or CDs. The people behind Grouper say they hope to eventually offer a premium service stripped of ads and the ability to control a PC from afar.

Although unauthorized versions of copyrighted material do sometimes drift across the network, the company says it makes great effort to distance itself from illegal activity.

"Our intent is not to circumvent the copyright world," said Josh Felser, a co-founder of Grouper. "This is about personally generated content."

Felser and other advocates of commercial darknets think they are fulfilling consumer demand for what might best be called personal distribution, a medium whose potential content expands with every video-equipped cell phone and pocket-size digital camera bought.

"The big play for us is personal video," Felser said last month, as he toyed with a moviemaking digital camera in his office in Mill Valley, Calif. "Personal video is everywhere, and people are wanting to share video that they create."

Fighting piracy
To prevent piracy, Grouper limits the file-sharing capacities on its network. Instead of letting members download music, for example, users are allowed to listen only to others' MP3s in real time through FM-quality streams. Grouper also limits groups to 50 people, and adds a whistleblower feature so members can call out illegal activity.

But their methods are not foolproof. Conspiring group members can change music file extensions or compress album folders to allow downloading, as does the group Only Zipped Music, and there is no means to block pirated software and crack codes, which are circulated in groups like Krakk'd, Warez and Xbox Gamez.

Felser and his partner, Dave Samuel, say they feel that their self-regulating efforts allow them to continue courting the media industry. "We want a company that gives us the ability to partner with other media companies, and eventually, an exit strategy," said Felser, who sold their previous enterprise, an Internet radio broadcaster called Spinner.com, to America Online for $320 million.

Qnext, another private peer-to-peer network, also tries to distance itself from illegal users in the hope of building a successful business without setting off legal battles. The company packages its service as an all-in-one communications tool with instant messaging, video conferencing and Internet

The Qnext software does not assist the development of groups of strangers, however, making it more difficult to disseminate copyrighted entertainment widely. A company spokesman, Simon Plashkes, said this limitation rendered Qnext useless as a piracy tool.

"If someone was sharing a movie, it would be hard to send that to more than five people," Plashkes said. "The technical design is not the best piracy platform."

Even in more public forums, like virtual communities, users increasingly want to share files as well as photos; administrators have responded by developing safeguards against misuse.

Imeem, a social networking group that connects users with common interests, encourages members to share files like videos and recordings among friends. But the company's owners say that by publishing the relationships among members and listing the membership of its groups, they are creating a deterrent to illegal trading.

"If you're letting people into your trust network, you're implicating them as well," said Dalton Caldwell, one of the service's co-founders. "It re-creates in the digital world the kind of pressure that exists in the real world."

It remains unclear whether these efforts will be enough to ward off a litigious entertainment industry.

"The protections are good, but unfortunately, that kind of argument is no longer as strong as it was prior to the Grokster case," said Lawrence Lessig, a Stanford University law professor, referring to a recent United States Supreme Court ruling that allows companies to sue peer-to-peer networks for copyright infringement if they are shown to encourage illegal downloading.

"If I were an investor, I'd think strongly about whether to invest in a company that could facilitate this sharing," he said.

Copyright owners make it clear that they are prepared to defend their turf. "We don't take issue with the technology," said Kori Bernards, a spokeswoman for the Motion Picture Association of America. "It's when it's for illegal uses. When they promote or facilitate this, they should be aware that they are accountable."

Bernards said that in the wake of the Grokster decision, the association had been approached by some file-sharing companies that wanted to learn if their operations were likely to attract copyright-infringement lawsuits.

Nor is Lessig alone in suggesting that the entertainment industry's vested interests may lead to efforts that will stifle technological innovation.

"The more Hollywood clamps down, the further underground the activity is driven, and the more difficult it's going to be to find out what's going on," said J.D. Lasica, author of "Darknet: Hollywood's War Against the Digital Generation."

Signs already exist that file-sharing networks are becoming more stealthy.

Ian Clarke, founder of Freenet, a peer-to-peer network meant to circumvent government efforts to censor material on the Internet, says he will soon unveil a version of his program that will coordinate private groups. Clarke said he viewed the spread of pared-down commercial darknets as a setback, that they gave up too much ground to copyright holders and limit what could otherwise be powerful software.

"These guys are deliberately holding back, and that's what happens when lawyers dictate software development," Clarke said. "Software people enable people. Lawyers disable people."