Some of the universities that have been targeted in the MPAA's investigation include Harvard University and the University of Connecticut. Meanwhile, ISP Excite@Home has sent out about 20 e-mails and letters over the past four days telling Gnutella users their services will be terminated within 24 hours if their alleged movie sharing continues.

The MPAA already has aggressively--and successfully--sued several companies, accusing them of aiding copyright infringement by allowing people to record and trade copyrighted content. They include Scour, iCraveTV.com and RecordTV.com. But until now, Gnutella systems have flown below the legal radar screen of many copyright holders, partly because it's so difficult to track infringement on systems that lack central servers.