"It's abundantly clear by now that no D.R.M. system can stop serious pirates," wrote Edward W. Felten, a professor of computer science and public policy at Princeton University, on his blog, Freedom-To-Tinker.com. "A D.R.M. system that stops serious pirates, and simultaneously gives broad leeway to ordinary users, is even harder to imagine."
Still, from the Microsoft Corporation's own Windows Media D.R.M. and Apple Computer's proprietary FairPlay technology to next-generation disc protection schemes like Macrovision's Total Play, SunnComm's MediaMax and even Sony's own DADC technology, a forest of overlapping and sometimes conflicting copy-protection and rights-management systems now attempt to govern the digital media experience.
Many technologies that allow limited CD ripping do not permit the creation of the popular MP3 file format, prompting some artists, including Switchfoot and Dave Matthews, to begin publishing instructions for circumventing their albums' copy protections on the Web, so that fans can move tracks that are nominally incompatible with Apple's FairPlay, onto the popular iPod music player.
Even Sony BMG, which is not licensed to distribute FairPlay-compatible tracks on its discs, posts such instructions on its Web site.
Of course, that is the kind of flexibility that fans want, Mr. Chanko of Jupiter Research said, and the challenge of digital rights management, he added, "is to engage the consumer in a way that makes them an ally."
Sony BMG seems to have failed that test when, in seeking to limit consumers to making three copies of its CD's, it embedded the First 4 Internet software, which penetrates deeply into the PC's of users with a program that introduced a real, if minor, security risk.
It all began unraveling early last month, after an American customer notified F-Secure, a Finnish antivirus company, of some files attempting to hide themselves on his computer. F-Secure deduced that the Van Zant CD had deposited a program that looked a lot like a "rootkit" - typically a dirty word in computer security circles because it describes software tools used to hack the deepest level of a computer system and hide the footprints of an intruder.
That might have been bad enough, said Mikko H. Hypponen, the chief research officer of F-Secure, but the rootkit also proved capable not just of hiding itself, but any file, folder or process on the computer that used a five-character string as part of its name.
No other file on a typical computer would have that string in its name. But if an enterprising virus writer managed to figure out the system, named his bug appropriately, and somehow got it onto the machine of a consumer whose only real sin was listening to Celine Dion's "On ne Change Pas" on his PC, Sony BMG's copy-protection software would cloak the worm.
In computer security terms, it is a tiny vulnerability, but as of last week it was clear that at least a few virus writers were attempting to exploit it.
"It was designed to be speed-bump technology," said Mathew Gilliat-Smith, the chief executive of First 4 Internet, meaning it would slow down those seeking to circumvent the copy restrictions.
F-secure quietly contacted Sony BMG and First 4 Internet with its concerns, but on Oct. 31, Mark Russinovich, a security expert at SysInternals.com, published his own discovery of the rootkit on his blog. Public outrage followed on the Internet as the program was further examined, the end user license agreement deconstructed, and Sony BMG's response scrutinized.
"We deeply regret any possible inconvenience this may cause," the company said in a statement on Friday. "We stand by content protection technology as an important tool to protect our intellectual property rights and those of our artists."
Unfortunately, the artists are suffering the fallout, too.
"Take your rootkit and shove it," was one angry message that Ross Schilling, the Van Zant manager, said was left on his voicemail.
"The Internet, downloading, file-sharing - it's a whole new Wild West for the music business," a somewhat weary Mr. Schilling said, adding that while he supports the idea of protecting content, he regrets that Van Zant has become the poster child for bad D.R.M. schemes.
"To some degree the labels have been slow to embrace things, and are now playing catch-up," he said. "They'll continue to tweak these systems, and everyone will have to pay attention more closely."

Nota: Esto me lo traje de un foro foraneo.