Anti-forensics of median filtering

A number of forensic techniques have been developed to identify the use of digital multimedia editing operations. In response, several anti-forensic operations have been designed to fool forensic algorithms. One operation that has received considerable attention is median filtering, since it can be used for image enhancement or anti-forensic purposes. As a result, several median filtering detectors have been developed. In this paper, we propose an anti-forensic technique to disguise the use of median filtering. We do this by first proposing a model for an unaltered image´s pixel difference distribution. We then modify a median filter image´s pixel difference distribution using anti-forensic noise so that it no longer contains median filtering fingerprints. Through a series of experiments, we are able to show that our anti-forensic technique can fool existing median filtering detectors under realistic conditions.