The lawsuits mark an expansion of the copyright holders' legal strategy in the file-swapping world, targeting sites that help make downloading easier, but aren't actually delivering the files or the swapping technology themselves.
It's also the first time the group has sued organizations that direct their members to the Usenet newsgroup system, an MPAA spokeswoman said. The movie group makes little distinction between a peer-to-peer network and the search engines that point to pirated works, saying that all facilitate the distribution of copyright works.
"Disabling these powerful networks of illegal file distribution is a significant step in stemming the tide of piracy on the Internet," John Malcom, MPAA director of Worldwide Antipiracy operations, said in a statement.
The issue of targeting search engines rather than actual file-swapping networks themselves has been a touchy one in Silicon Valley, because ordinary search engines such as Google and Yahoo also can be used to find pirated works.
The Digital Millennium Copyright Act protects search engines from liability for linking to pirated works, but only if the site operators don't know that the specific content is infringing, are not deriving financial gain from the links, and act quickly to remove the links when contacted by copyright holders.
Unlike a traditional search engine such as Google, the sites targeted Thursday are filled almost exclusively with links and references to copyright movies, software and music.
IsoHunt, one of the largest search engines targeted, does provide a copyright statement that says, "We respect copyright, and will filter such P2P links at your request."
The full list of sites sued Thursday include Torrentspy.com, IsoHunt, BTHub.com, TorrentBox.com, NiteShadow.com, Ed2k-It.com, NZB-Zone.com, BinNews.com and DVDRs.net.
Electronic Frontier Foundation attorney Fred von Lohmann said that the courts had not yet ruled on whether search tools could be held liable for copy infringement. Most relevant cases, such as record labels'several years ago, have been settled before the issue has come to trial, he said.
"We haven't had a case that really tests the case of whether providing an indexing service by itself an infringement," von Lohmann said.
Thursday's suits are part of a growing series of lawsuits, criminal and civil actions taken around the world, as the movie industry works to stamp out the still-strong growth of film and TV show swapping online.
The MPAA has had a string of successes targeting sites that distribute movies in the BitTorrent file format, shutting down popular hubs such as Suprnova, LokiTorrent, and others. Earlier this week, the Hollywood announced that it had collaborated with Swiss and Belgian police to shut down a major European server called Razorback 2, part of the eDonkey network, which was allegedly used by as many as 1 million people.
File-swapping traffic has continued to grow globally throughout the course of the legal actions, however. Net monitoring firm CacheLogic estimates that P2P still accounted for more than 60 percent of overall Internet traffic at the beginning of 2006, with video files accounting for about 60 percent of that data.
Traditional peer-to-peer software companies such as eDonkey and Lime Wire have not been targeted by lawsuits in recent months. However, they have faced warnings from record labels and the MPAA thatif they continue to allow unregulated swapping online.
The MPAA previously announced an agreement with BitTorrent.com, the creators of the BitTorrent file-swapping technology who also run a file search engine. Under that agreement, BitTorrentin its search tool.