Due to the drastic development of Internet, it has recently been a critical problem to secure multimedia contents against illegal use. In order to solve this problem, data hiding has drawn great attention as a promising method that plays a complementary role to conventional cryptographic techniques. The idea of this approach is found in ancient Greek literature as 'Steganography,' which means a 'covered writing' for special secret communication. This paper presents a new method for steganographic image transformation, which is different from conventional data hiding techniques. The transformation is achieved in frequency domain and the concept of Fourier filtering method is used. An input image is transformed into a fractal image, which can be used in Computer Graphic (CG) applications. Unauthorized users will not notice the 'secret' original image behind the fractal image, but even if they know that there is a hidden image it will be difficult for them to estimate the original image from the transformed image. Only authorized users who know the proper keys can regenerate the original image. The proposed method is applicable not only as a security tool for multimedia contents on web pages but also as a steganographic secret communication method through fractal images.