LOS ANGELES - Turning the tables on record labels, makers of the most popular Internet song-swapping network are suing entertainment companies for copyright infringement. Sharman Networks Ltd., the company behind the Kazaa file-sharing software, filed a federal lawsuit Monday accusing the entertainment companies of using unauthorized versions of its software in their efforts to root out users. Entertainment companies have offered bogus versions of copyright works and sent online warning messages to users. Sharman said the companies used Kazaa Lite, an ad-less replica of its software, to get onto the network. The lawsuit also claims efforts to combat piracy on Kazaa violated terms for using the network. Sharman's lawsuit also revives its previous allegation that the entertainment companies violated antitrust laws by stopping Sharman and its partner from distributing authorized copies of music and movies through Kazaa. U.S. District Judge Stephen V. Wilson rejected those claims in July but last week allowed Sharman to try again. Sharman is incorporated in the South Pacific island nation of Vanuatu with main offices in Sydney, Australia. The Recording Industry Association of America (news - web sites) called Sharman's "newfound admiration for the importance of copyright law" ironic and "self-serving." Universal Music Group and Warner Music Group declined to comment on Sharman's latest lawsuit. Recording companies sued 261 music fans this month, claiming they were illegally distributing hundreds of digital song files apiece over the Internet. The industry trolled file-sharing networks such as Kazaa and downloaded song files from users' computers. Once the industry determined a downloaded song file was a copyright work, they issued subpoenas to Internet access providers to find out who was behind the account used to log onto the file-sharing network. Meanwhile, the recording industry group has dropped one of the 261 lawsuits, a case filed against a 66-year-old sculptor who apparently was targeted in a case of mistaken identity. Sarah Seabury Ward, of Newbury, Mass., was accused of illegally sharing more than 2,000 songs through Kazaa, including rapper Trick Daddy's "I'm a Thug." The music companies threatened to hold her liable for up to $150,000 for each song. After Ward's lawyer complained that Ward is a "computer neophyte" who never installed file-sharing software or downloaded any songs, the case was dropped in federal court in Boston on Friday.