The music business is bringing its battle with file sharers to end-users' desktops.

The industry is using the instant-messaging features built into popular file sharing applications to tell users that sharing copyrighted material is illegal.

Recording industry groups, including the Recording Industry Association of America Inc. (RIAA), the American Federation of Musicians and the Christian Music Trade Association, started sending long messages headlined "Copyright infringement warning" on yesterday, according to the RIAA.

In the message, file sharers are told they are not anonymous, that they risk "legal penalties" and that their actions hurt songwriters, musicians and all music industry employees. Furthermore, the message warns that file-swapping applications may make a computer vulnerable to hacker attacks and expose private files.

The message reads: "It appears that you are offering copyrighted music to others from your computer. Distributing or downloading copyrighted music on the Internet without permission from the copyright owner is illegal. It hurts songwriters who create and musicians who perform the music you love, and all the other people who bring you music.

"When you break the law, you risk legal penalties. There is a simple way to avoid that risk: don't steal music, either by offering it to others to copy or downloading it on a "file-sharing" system like this.

"When you offer music on these systems, you are not anonymous and you can easily be identified. You also may have unlocked and exposed your computer and your private files to anyone on the Internet. Don't take these chances. Disable the share feature or uninstall your "file-sharing" software.

"This warning comes from artists, songwriters, musicians, music publishers, record labels and hundreds of thousands of people who work at creating and distributing the music you enjoy. We are unable to receive direct replies to this message. For more information about this Copyright Warning, visit"

Sending these messages is part of the recording industry's "educational efforts," the RIAA said. Many users of applications such as Kazaa, Morpheus and Grokster may be under the mistaken impression that anything they do on these systems is legal, the RIAA said. However, some users may never get the recording industry's message, as it is simple to turn off messaging in Kazaa.

The messaging action comes after a court ruling last week that two providers of free file-swapping software can't be held liable for the copyright infringing actions of their users, a major setback in the recording industry's fight against file sharing.

The industry appears to be stepping up its actions against individual file swappers, even though analysts have said that suing individual users may backfire. Earlier this month the RIAA sued four students who allegedly ran file-sharing networks on their school's local networks.

The RIAA and other entertainment industry organizations have been battling online piracy in court for years. They compare online sharing of copyright protected music, movies and software to shoplifting.