Abstract: Image authenticity is a real issue in the digital forensic field since the wide spread of images and the spread of low-cost image processing software which make it easy to alter images and change them using hard to detect techniques. This study highlights the importance of image authentication and on which level a JPEG image could be altered. Also, it covers some techniques used in making forged images. Finally, it discusses some current techniques used in detecting and localizing forgeries in JPEG images.