Samuel Johnson once said that "music is the only sensual pleasure without vice." Evidently, Mr. Johnson was not a punk rocker. And had there been something like Napster in the 18th century, he surely would have viewed music in a different light.

These days, for the estimated 40 million Americans who trade songs over the Internet, music and vice go hand in hand. After all, much of this music is copyright protected. The recording industry did successfully shut down Napster, mother of all song-swapping sites, for contributing to copyright infringement. But stifling the next generation of file-trading programs such as Kazaa, Morpheus, and LimeWire has proven more difficult. Unlike Napster, these are truly open networks that connect traders directly with each other. For the recording industry, these peer-to-peer networks are a high tech Wild West.

What's at stake? Plenty, according to a recent report by the Recording Industry Association of America, which represents the major record labels. Last year, shipments of full-length compact discs slipped by about 6 percent-the worst decline in a decade. Nearly one-quarter of the music consumers the association surveyed admitted to illegally downloading music rather than buying new CDs. The study also found that ownership of CD "burners" (disc drives that can record music onto blank CD-ROMs) has tripled since 1999; two out of five music consumers now own the machines. According to the International Federation of the Phonographic Industry, music piracy, including nearly one billion black-market CDs, cost the industry $4.3 billion last year.

Against such odds, the industry is bracing to deliver what could be a lethal counterpunch: new technologies that provide copy protection at the root of the problem, the compact disc. "We're looking for ways that will maintain the personal copying capability that consumers want," says Recording Industry Association of America president Cary Sherman, "without taking the risk of unlimited copying."