Abstract—Steganography is a hiding system that conceals the information in a way only the sender and the recipient know about its existence. Various steganography methods developed to cover different objectives of steganography applications. All these objectives support the main goal of steganography that is undetectability. In this paper a DCT based steganography system is proposed to embed information in 4th bits of DCT coefficients and optimize quality of the obtained stego-images applying genetic algorithm that looks for the best position for embedding. The main idea is derived from SSB-4 method which embeds the message in more significant bits to be more resistant against various steganalysis methods. The experimental results show that the proposed method enhances the imperceptibility and undetectability of the stego-images and is resistant against some steganalysis techniques such as chi-square attack.