Hollywood's Internet piracy crackdown has caused a sharp drop in "OpenNap" servers - computers that run Napster-like software but are not associated with the song-swap service, a recent research report shows.
"OpenNap servers fell by over 75 per cent in the period from late February to late April 2001," said Mr Kelly Truelove, founder and chief executive of Clip2, which tracks peer-to-peer networks.
Mr Truelove wrote that the number of simultaneous users among these servers declined from 100,000 in late March to less than 50,000 by late April, and the number of files available similarly dropped about 50 percent from its peak in March.
"The decline in these servers may be result of the Recording Industry Association of America's (RIAA) decision to send letters of complaint to Internet Service Providers (ISP) providing service to users operating OpenNap servers," he said.
Preventing online piracy has become a crusade for the music and film industries with the explosion of file-sharing services like Napster, which is currently operating under a court-ordered injunction against traffic in copyrighted material.
Shortly after an appeals court ruling in February that paved the way for the injunction against Napster, the RIAA sent out dozens of legal notices to ISPs providing connections for "Open Napster" servers.
The Motion Picture Association of America (MPAA), a trade group for the major studios, also sent hundreds of letters to ISPs in April, warning them some of their users were violating the Digital Millennium Copyright Act (DMCA) by trading movies through the Gnutella file sharing system.
Gnutella systems have been hard to target because they don't use central servers and pass along files through a chain of individual computers. The movie industry must, therefore, rely on ISPs to help it hunt alleged infringers.