A system and method is provided for encoding an identifiable code into the audio content of a motion picture. The audio content is altered in at least one specific pre-selected location in the audio soundtrack of the motion picture so as to be essentially unnoticeable to the listener. The audio content is altered to form an audio code which represents a unique number applied to that copy of the motion picture, whereupon any audio recording of such audio content would capture the audio code. The unique number is stored together with an identification of the location, entity or person who receives the copy when it is distributed, so as to enable suspected counterfeit copies of the motion picture to be analyzed to read the code number and identify the recipient of the copy and thereby track down the source of the counterfeit copies.