Cactus Data Shield claims to offer:

• Prevents any type of unauthorized digital duplication of CDs, DVDs and proprietary formats (Music, Video or Data).

• It does not rely on software keys, hardware dongles, plugs or other external equipment or processes.

• Protected CDs and DVDs fully operate on existing commercial players and drives.

• It prohibits Internet-piracy by preventing unauthorized transmission/conversion of digital files (Music/MP3, Software and Video) over the Internet.

There where some reports that this protection could damage hi-fis and loudspeakers but as it seems now this was just a rumor:

Cactus inserts modifications to original CDs in a way that confuses CD-ROM devices during the copying process. Midbar assures us that it regards any technology that has the potential to damage any hi fis and/or loudspeaker equipment as totally unacceptable, and has asked us to make clear that there is nothing in its technology on the market, past, current or future, that could, or would, be potentially damaging to equipment.

Midbar says record labels have released more than one million CDs protected by its Cactus system into the European market--with no complaints.