An active shutter device for use in securely displaying content from a display to a user. The secure content is encoded as a sequence of video frames interspersed within a set of video frames, at least some of the other frames within the set including obfuscating data. The device comprises a receiver for receiving a synchronization signal, at least one shutter mechanism, and a processor. The processor, in response to the synchronization signal, controls the shutter mechanism so as to synchronize the shutter mechanism with, for example, the refresh rate or the video frame display rate of the display. The processor is configured to receive a frame sequence corresponding to the sequence of video frames used of the secure content, and control the shutter mechanism, in response to the received frame sequence, to allow only the video frames in the secure sequence to pass through the shutter.