Apple's iTunes allows Macintosh and PC users to play music stored on other PCs on a network. The music is streamed off the other computer. But file-swapping enthusiasts quickly created other programs, such as MyTunes, to capture the songs and allow them to be saved to the computer's hard drive.
With the latest iteration -- version 4.5 -- Apple appears to have plugged that hole.
An Apple representative on Wednesday confirmed that with the new version of iTunes, the company has "strengthened" the music-sharing feature to make sure that song sharing is limited to personal use and that only another copy of iTunes can access the music stream.
Also, once iTunes users have upgraded to the newest version of the software, they are no longer allowed to stream music from computers running older versions of iTunes.
Apple imposed a similar restriction earlier, after some people used the music-sharing feature to swap files over the Internet.
MyTunes creator Bill Zeller said he was somewhat surprised by Apple's move.
"It seems like a big step to make all previous versions incompatible," Zeller said in a telephone interview. "It was nice while it lasted."
The Trinity College sophomore said it appears that Apple tweaked its communications protocol to prevent MyTunes from capturing the song streams.
"I would assume that they changed the protocol in some way, which would make it not work," Zeller said.
Although someone could create an updated program that tries to capture the streams, Zeller said it won't be him. Last month, a massive computer crash took with it his only copy of the MyTunes source code.
"Someone else could come up with a program to get around the restriction," he said.
The iTunes content protection technologies have been the subject of continual attacks by programmers looking to evade Apple's restrictions on sharing.
While Zeller's program took advantage of the software's streaming capabilities, other programmers have worked to strip out the anti-copying features, called FairPlay, included with every song purchased from the iTunes store.
Several programmers have created software that does appear to remove the FairPlay protections altogether, allowing the purchased songs to be distributed without restriction. Jon Johansen, the Norwegian youth who first released the DeCSS DVD-copying tool online, has led this drive, with the tools he has developed winding up in several other pieces of software.
While Apple has worked to keep some of these applications, including the recent anonymously released "PlayFair" offline, some record label executives have said the impact has been low, because consumers can still burn CDs from iTunes songs and re-rip them into unprotected MP3 form. Johansen said the project has been worthwhile, however.
"Burning a CD and ripping the music back to a compressed format takes time and results in loss of quality," Johansen said in an email interview, noting that Apple's restrictions on copying remained a deterrent to iTunes purchases for some people. "Using a decryption utility like PlayFair takes only a few seconds per song and does not result in loss of quality."
CNET News.com's John Borland contributed to this report.
