In this paper, we proposed a categorization for most of the existing watermarking algorithms that work in wavelet domain. Then an adaptive watermarking attack for digital images that is based on the proposed categorization is presented. This attack determines the flat regions, edges and textures of the watermarked image and based on known features of each region the proposed attack tries to destroy the watermark information by manipulating the wavelet coefficients of each region separately such that the least visual distortion will be imposed on the attacked image. We have tested the proposed method to attack two recent and robust watermarking methods and the results sound impressive. The average PSNR of the watermarked image after applying the proposed attack is more than 31 dB and the average NC for extracted watermark is lowers than 0.4, so the watermark is not detectable. The proposed method does not consider any knowledge about the underlying watermarking algorithm.

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