A machine-non-readable defect is formed on a CD-ROM by re-modulation of a master cutting laser beam recorder. Re-modulation in specific program areas creates non-readable marks which interfere with any attempt to image-copy the CD-ROM. The non-machine-readable marks can be followed by valid data which...http://www.google.de/patents/US6646967?utm_source=gb-gplus-sharePatent US6646967 - Method for making copy protected optical discs
