you are correct, but the noise cannot be mere single pixel "speckle" in 2020, and needs to be both lumen and color varied size dots, to do that in gimp merely blow up a 1/4 size layer of random noise, or a 1/8th layer of random noise, so that its no longer "single pixel" sized noise. Even still, it can not trick many detectors that reduce image to 64x64 for part of its logic.