The letter follows some discussion between the states' top law enforcers and the companies themselves. The companies requested a dialogue after alast spring. That letter was similarly critical of the file-sharing firms.
Thursday's letter asked makers of file-sharing software to take "meaningful steps" to prevent the dissemination of child pornography, invasion of privacy and copyright infringement. The group stopped short of citing specific legal action that states might take against companies but said they could target individuals using file-swapping networks for fraudulent purposes.
"We are writing to encourage your companies to take concrete and meaningful steps to address the serious risks posed to the consumers of our states by your companies' peer-to-peer file-sharing technology," the letter said. "At present, P2P software has too many times been hijacked by those who use it for illegal purposes, to which the vast majority of our consumers do not wish to be exposed."
File-sharing companies, which have long been criticized by big entertainment companies for allowing unrestrained trade in copyrighted works, have more recently come under fire for broader issues.
Although there is little evidence that child pornography or other criminal activities unrelated to copyright issues are any more prevalent on peer-to-peer networks than elsewhere on the Internet, entertainment companies and some policymakers have increasingly pointed to these issues as reason to impose new regulations on the networks and technology.
In Washington, Sen. Orrin Hatch, R-Utah, is sponsoring a bill that would for the illegal actions of their users, a measure that could push the existing commercial networks out of business.
The state attorneys general have been looking at this issue for much of the year and have been consulting entertainment groups, including the Motion Picture Association of America.
In their letter, the attorneys general echo many of the sweeping complaints made by entertainment companies, saying as one example that peer-to-peer networks are replacing e-mail and online chat rooms as the favored haunts of child pornographers.
The letter specifically asks that file-sharing companies stop encrypting network transmissions in ways that make it difficult for law enforcement to investigate and enforce the law. The group also asks that the companies stop bundling spyware and adware with their software, and add filters that can block offensive materials.
The letter makes some technical claims that are difficult, if not impossible, to support, including a claim that a computer that is "off" can continue swapping files over a broadband connection.
Peer-to-peer companies say they have tried to work with the attorneys general since learning that the group was interested in the issue. Representatives of file-sharing companies and entertainment companies each spoke at the attorneys general national meeting in June.
Peer-to-peer executives say their voices have been drowned out by the lobbying of entertainment companies, however.
"This appears to be a case of contempt prior to investigation," StreamCast Networks CEO Michael Weiss said. "This appears to be a continuation of the lies and deceit being perpetrated by the entertainment industry against P2P companies to Congress, the American public and now the offices of the attorneys general."
Marty Lafferty, chief executive of the Distributed Computing Industry Association, another peer-to-peer group, said he has seen what appeared to be a draft of the current letter and that it contained substantial mischaracterizations of the technology and the file-swapping networks.
"We want to meet with (the attorneys general) and see if they'll go through and separate the totally false allegations from those things where there might be something we could respond to," Lafferty said. "This is all part of a smear campaign by major labels and studios."
News of the letter was first reported by The Washington Post.