We propose a sinkhole detection method for mobile ad hoc networks (MANETs). MANETs are vulnerable to various network attacks. A sinkhole attack is a sort of routing protocol attack which can spoil all network connections in MANETs. The proposed method considers the sinkhole problem in the context of Dynamic Source Routing (DSR). In this study, we analyzed the sinkhole attack and extracted features when a sinkhole attack occurs. Then, we developed a cooperative detection method using the analyzed features. The proposed method was designed to improve performance in terms of detection rate and detection time. The simulation results show that the proposed method is effective and reliable for detecting sinkhole attacks. (C) 2009 Elsevier GmbH. All rights reserved.