A method for protecting data recorded on an original storage medium against unauthorized copying. The data are encoded in accordance with Standard 908 of the International Electrotechnical Commission. A portion of the encoded data is altered to introduce an error in a sub-code Q channel of the data, such that the altered data are inconsistent with Standard 908, but do not prevent playback of the data following recording thereof. The data, including the altered data, are recorded on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.