A Method for Detecting JPEG Anti-forensics.

In this paper, a new approach is proposed for the detection of JPEG anti-forensic operations. It is based on the fact that when a JPEG anti-forensic operation is applied, the values of DCT coefficients are changed. This change decreases, especially in high frequency subbands, if we apply anti-forensic operation again. Hence, we propose to calculate a normalized difference between absolute values of DCT coefficients in 28 high frequency AC-subbands of the test image and its anti-forensically modified version. Based on this normalized feature, it is possible to differentiate between uncompressed and anti-forensically modified images. Experimental results show the effectiveness of the proposed method.