How can one distinguish between fake and actual photos/videos

So in this deep learning module, we are learning to use CNNs to identify images. I have this use-case, where the system needs to distinguish between fake and real images. For ex. in a security system (or face detection based attendance system), the algorithm should be able to prevent photo/video attacks, i.e. distinguish between fake photos/videos and real person. Can I get some guidance to develop such a module?