Sensor nodes that are deployed in hostile environments are susceptible to capture and compromise. An adversary may gain private information from these sensors, clone and logically deploy them in the network to launch a variety of insider attacks. This attack process is generally termed as a clone attack. Currently, the defenses against clone attacks are not only very few, but also suffer from selective interruption of detection and high overhead (computation and memory). In this paper, the authors propose a new effective and proficient scheme, called SET, to identify such clone attacks.