Cactus Data Shield

Cactus Data Shield (CDS) is a form of CD/DVD copy protection for audio compact discs developed by Israeli company Midbar Technologies now owned by TiVo Corporation. It has been used extensively by EMI and BMG and their subsidiaries. CDS relies on basically two components: Erroneous Disc Navigation, and Data Corruption.

As of September 2006, all of Macrovision's CD copy protection products, including CDS, had quietly disappeared from their website. [1] The December 2006 issue of Billboard announced that EMI had decided to abandon Copy Control worldwide.

CDS discs contain an initial audio session, similar to that of an unprotected disc. In addition the disc contains a second (data) session and a software player configured for auto-play with a lower-quality, compressed version of the audio for it to play.

The second session on the disc causes some CD/DVD players to hang, typically some car players (allegedly using CD-ROM drive mechanisms) and some MP3 capable players that can see but not understand the second data session.

The second session has been circumvented by another method, which is to either place masking tape around the disc near the edge, or mark a strip next to the edge with permanent marker. Because it is a multi-session disc, this method will hide the second session, leaving only the first audio session visible.

On older Windows operating systems, disabling auto-play either once when loading the disc, or permanently, can stop the software player from launching and may be all that is required to access the audio session for drives that recognise both sessions. Newer versions of Windows since Vista have fixed the auto-run vulnerability thus all the user needs to do is simply choose not to run the software.

A side effect of the second session containing the music in compressed form is that the maximum length of music on a CDS disc is reduced, being approximately 70 minutes. The remaining space is use for the compressed audio (and the player software and other files though these are small by comparison).

The second aspect of Cactus Data Shield is careful corruption of the audio data, as described in the Midbar patent "Prevention of disk piracy" US patent number 6,425,098. As usual for patents this is freely available on the US Patent Office web site.

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