A copy protection technique is described which enables the content (14) of an application file (4, 20), for example, provided by a licensed game provider, to be copy protected without action having to be taken at the time of encoding the application file onto a DVD or other optical disc. DSV data patterns, that is data patterns which are difficult to encode without causing DSV problems, are to be incorporated in the application file (4, 20). It is expected that sophisticated encoders (8) at games console manufacturers will be able, for example, by using look-ahead techniques, to encode and apply the application to the glass master (10) in a manner such that the encoded data will not cause DSV problems. However, if an attempt is made to read the data on the original disc, for example, for copying purposes, the DSV data patterns will cause a CD or DVD writer to encode the data onto the copy disc in a manner which renders the resultant copy disc effectively unplayable. The DSV data patterns may be incorporated in an application file (20) within information, or in control data therof (FIG. 5).