The dynamic and cooperative nature of ad hoc networks presents substantial challenges in securing and detecting attacks in these networks. A particularly severe security attack, called the wormhole attack, has been introduced in the context of ad-hoc networks. During the attack, a malicious node captures packets from one location in the network, and tunnels them to another malicious node at a distant point, which replays them locally. In this paper we survey and classify the solutions that have been proposed in the literature for this attack and propose a decentralized scheme for intrusion detection based on the theory of diffusion of innovations. We argue that the proposed approach is more appropriate to address ad hoc networks’ dynamic and cooperative nature especially at the application level.