Identification of LSB image Steganography using Cover Image Comparisons

Steganography has long been used to counter forensic investigation. This use of steganography as an antiforensics technique is becoming more widespread. This requires forensic examiners to have additional tools to more effectively detect steganography. In this paper we introduce a new software concept specifically designed to allow the digital forensics professional to clearly identify and attribute instances of least significant bit (LSB) image steganography by using the original cover image in side-by-side comparison with a suspected steganographic payload image. This technique is embodied in a software implementation named CounterSteg. The CounterSteg software allows detailed analysis and comparison of both the original cover image and any modified image, using sophisticated bitand color-channel visual depiction graphics. In certain cases, the steganographic software used for message transmission can be identified by the forensic analysis of LSB and other changes in the payload image. This paper demonstrates usage and typical forensic analysis with eight commonly available steganographic programs. Future work will attempt to automate the typical types of analysis and detection. This is important, as currently there is a steep rise in the use of image LSB steganographic techniques to hide the payload code used by malware and viruses, and for the purposes of data exfiltration. This results because of the fact that the hidden code and/or data can more easily bypass virus and malware signature detection in such a manner as being surreptitiously hidden in an otherwise innocuous image file.