One of the most controversial topics of the past few years has been the debate over the legality of internet-based services such as Napster, KaZaA, and Morpheus. The very essence of these services is to provide their user with free mp3 song files. These files can then be played on the user's computer or "burned" to a blank CD and then played in all manner of CD players. In an effort to stop this alleged piracy, the Universal Music Group has created a new type of CD from which the songs cannot be "ripped" into mp3 format, and therefore cannot be shared across the internet. The problem is that the same measures that prevent the copying of the music files also render the CD useless in other ways. The copy-protected CD will not play on Macintosh computers, and even on some home CD players. A possible way to fix this problem is a "dual-session" CD, which has two complete sets of tracks. One set plays in home stereos, while the second session is digitally encrypted with rights-management technology that limits the number of copies a consumer can make. The fact that the encryption only limits copying and does not prevent it is crucial; buyers can still make copies for personal use, "but it would discourage 15 high school students from getting together and pooling their money to buy a single music CD and a spindle of blank discs and making dubs for everyone in the group - with a few extras to sell at school." The fact that the encryption of the CD prevents the CD from working in some players signals a return to the drawing board. If they hope to use such technology, the record companies must find a way to design the disc with these dual sessions, yet be compatible in all commercial players.