At last, there's a business model for Gnutella's rough-and-tumble world of file-swapping: spam.

For the last several weeks, a company known as Flatplanet.net has been hijacking Gnutella searches online, responding to queries on the network with ads for its software—a product that allows its customers to post their own ads on the Gnutella network. Unsolicited advertisements for such things as pornographic Web sites have appeared on the Gnutella network. But because the Flatplanet ads are more sophisticated than earlier Gnutella advertisements, and because they promote a product designed for creating new ads, they have sent ripples of concern through the loosely organized open-source community. "This wouldn't be the first time that Gnutella has been spammed," said Gene Kan, one of the developers who has taken a lead in the Gnutella development world. "But it's the first time there's been a commercial effort targeted at people who want to spam Gnutella." Although the Flatplanet Web site has been temporarily taken down by its network service provider after complaints about its software, the issue has set off a debate about how the file-sharing world can protect itself from advertisers. The Gnutella technology, originally developed by programmers inside America Online's Nullsoft, works much like Napster but without a central server. A computer running the program connects directly to a handful of other computers, each of which are connected to another handful, creating a daisy chain of members that quickly becomes enormous.