Techniques described herein generally relate to methods, data processing devices and computer readable media to ensure that data stored in a remote backing storage device are in encrypted form before that data is transferred to another device or over a network. In some examples, the methods, data processing devices and computer readable media may be arranged to encrypt the data passed to the network when the data stored in the backing storage device is in unencrypted form. Also disclosed are methods, data processing devices and computer readable media that identify when the data stored in the backing storage device is in unencrypted form, including methods that may detect that the data may appear to be in encrypted form as a result of the data being compressed.