Patent ID: 7761706

Claim:
A method for controlling access to digital rights management (DRM) protected content that is to be protected from unauthorised access, the method comprising: loading a DRM client responsible for temporarily decrypting and rendering the DRM-protected content, the DRM client being provided separately to the DRM-protected content; if not already loaded, loading code for executing an operating system service into memory; if the operating system service is operable to enable unauthorised access to protected content when the DRM client is handling said content, obtaining an address of an entry point of the loaded code in memory, and when the DRM client is handling decrypted DRM-protected content, placing, within the loaded code and starting at the entry point address, a replacement instruction such that, when the operating system service is to be executed the replacement instruction is executed in place of the operating system service, the replacement instruction causing substitute code to be executed, the substitute code operating to restrict or deny access to the DRM-protected content.