BitTorrent has become a widely used online system to get hold of very large video files as the technology is very efficient at splitting up and sharing data.

Use of the technology has proved to be a thorn in the side of the MPAA as it can make it hard to work out who is behind illegal movie sharing.

Links issue

As part of its efforts to tackle the issue, the MPAA has targeted websites which point to BitTorrent links such as Torrentspy.

Torrentspy stands accused of helping copyright infringement to occur by directing people to sites, some of which host copyrighted content which can be downloaded illegally.

In response, Torrentspy has filed a motion to dismiss the lawsuit in the federal court in Los Angeles.

It challenges that the allegation made by the Motion Picture Association of America that linking to torrent sites constituted secondary copyright infringement.

Torrentspy's lawyer Ira Rothken said the motion argued that Torrentspy does not link to Hollywood's copyrighted works.

He said Torrentspy had cooperated with Hollywood in removing objectionable links to torrent files and did not actively promote copyright infringement.

"It cannot be held 'tertiary' liable for visitors' conduct that occurs away from its web search engine," said Mr Rothken.

He said the MPAA was going beyond a recent ruling by the Supreme Court that file-sharing services could be held liable for actions of their users in certain circumstances.

"This appears to be the first case where major Hollywood studios are suing a search engine that does not even link to any files copyrighted by Hollywood.

"The MPAA is in essence trying to outlaw the torrent file format."

US lawsuits

This latest legal twist in the ongoing conflict between the media industries and file-sharing networks.

In November last year, the global recording industry launched its largest wave of legal action against people suspected of sharing music files on the internet.

It targeted 2,100 alleged uploaders using file-sharing networks in 16 nations including the UK, France, Germany and Italy.

File-sharers in Switzerland, Sweden, Argentina, Singapore and Hong Kong were also facing cases.

Thousands of people have agreed to pay compensation since the campaign began.

The number of cases brought by the International Federation of the Phonographic Industry (IFPI) outside the US since March 2004 now stands at more than 3,800.

In the US, civil lawsuits have been brought against more than 15,597 people since September 2003 and there have been at least 3,590 settlements.