CSS Explained

The "Hollywood" DVDs you buy or rent are protected with an encryption system called CSS (Content Scrambling System). The movie is stored in a scrambled format and can only be read by hardware or software that knows how to decode it. This scrambling system is what prevents you from simply copying a DVD to your hard drive for later viewing.

The manufactures of DVD players know the "secret logic" needed to decode a DVD. In fact, this logic is no longer a secret. A programmer named Jon Johansen (a fifteen year old boy from Norway) is generally credited with figuring out the logic needed to decrypt a CSS protected DVD. This information has been widely published on the Internet and has been incorporated in software programs called "rippers".

The Basics CSS Explained Rippers Macrovision Regions Dual Layer Blank Media
System Requirements