Peer-to-peer software vendors must re-engineer their software to prevent illegal file trading, and they must do a better job of warning users of the dangers of trading illegal files, said a letter sent by attorneys general from 47 U.S. states and territories to P2P vendors Thursday.The letter, signed by the attorneys general of California, Texas and Florida and others, calls for P2P vendors to also warn users about the amount of pornography traded through P2P software, including child pornography. "P2P users need to be made aware that they are exposing themselves, and their children, to widespread availability of pornographic material when they download and install P2P file-sharing programs on their computers," the letter says.The attorneys general also accuse P2P software of hurting their economies by encouraging illegal file trading, quoting the Business Software Alliance and the Motion Picture Association of America (MPAA) as saying piracy costs their industries billions of dollars each year. The letter notes that some P2P vendors have taken steps to warn users about using the software to illegally trade files. "However, more needs to be done by your companies to warn your P2P users as to the specific legal and personal risks they face when they use P2P technology for the illegal ends of disseminating pornography and 'sharing' copyrighted music, movies and software," the letter says.The letter notes the attorneys general will take action against P2P users who illegally trade files. Law enforcement actions against P2P users don't "excuse your companies from avoiding software design changes that deliberately prevent law enforcement in our States from prosecuting P2P users for violations of the law," the letter says.Representatives of P2P vendors took issue with parts of the letter. P2P United, a P2P trade group, is working with the Federal Trade Commission to better educate and warn users of potential problems with using P2P software, said Adam Eisgrau, executive director of the group. "This is not a new issue, and it's something we'll continue to work on," he said.But the letter's call for P2P vendors to redesign their software, such as including centralized content filters, would cause the "neutering" of the potential of P2P, Eisgrau added. "That cannot be done without radically changing the innovative nature of this software," he said.With 47 attorneys general signing the letter, Eisgrau's group takes the complaints seriously, he said. But Eisgrau suggested copyright debates are best worked out in\u00a0Congress, not in the states.Instead of focusing on outlawing P2P software, the entertainment industry should work with P2P vendors to distribute their products, added Marty Lafferty, chief executive of Distributed Computing Industry Association (DCIA), a trade group representing the Kazaa P2P software. "They haven't yet changed from trying to kill the technology to embracing it and trying to harness it," he said.Lafferty called the letter an "unfortunate distraction" in the DCIA's effort to reach compromise with the entertainment industry.The letter was sent to P2P United, the DCIA, Grokster, Lime Wire, and Sharman Networks, the owners of the Kazaa file-sharing software, among other P2P vendors.