Neural networks can be trained to identify the difference, but I don't know how specific that is to the generating model. In fact, the GAN technique, at a high

Neural networks can be trained to identify the difference, but I don't know how specific that is to the generating model. In fact, the GAN technique, at a high level is two networks -- one trying to distinguish the difference and one trying to create images that cannot be distinguished. That is the "adversarial" aspect. It is an interesting question that there may be some simple pre-processing techniques (edge detection, Fourier transform, etc) that more easily distinguish the image as a fake. Something like a shortcut from training a network to make the distinction.