Copy-Move forgery , in which a part of a digital image is copied and then pasted to another portion of the same image in order to conceal an important object in the scene, is one of the common image forgery techniques. This paper describes an efficient and robust algorithm for detecting and localizing this type of malicious tampering. Firstly, Discrete Wavelets Transform (DWT) is applied to a tampered image, then the low-frequency component in wavelet sub-band is divided into overlapped blocks. Seven statistics of each block are calculated which are lexicographically sorted so that duplicated blocks are identified by searching for rows that get closer to other rows after sorting. Through finding out the duplicated region in the wavelet sub-band , we can find out the duplicated region in the tampered image. Simulation results show the efficiency of proposed algorithm.