With the latest version (4.5) of iTunes, it seems that Apple have plugged the hole that allowed network file swapping.
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, after some people used the music-sharing feature to swap files over the Internet.
MyTunes was the software that took advantage of that hole and the 4.5 version of iTunes tweakes its communications protocol to prevent MyTunes from capturing the song streams.
The iTunes content protection technologies is now a challenge for programming and cracking enthusiasts to evade Apple's restrictions on sharing.