Watermarking algorithms needs properties of robustness and perceptibility. But these properties are affected by different -2 types of attacks performed on watermarked images. The goal of performing attacks is destroy the information of watermark hidden in the watermarked image. So every Algorithms should be previously tested by developers so that it would not affected by attacks.
@article{arxiv.1407.4738,
title = {Analysis of Attacks on Hybrid DWT-DCT Algorithm for Digital Image Watermarking With MATLAB},
author = {Lalit Kumar Saini and Vishal Shrivastava},
journal= {arXiv preprint arXiv:1407.4738},
year = {2015}
}