Security issues in Wireless sensor networks (WSNs) mainly come from attacks. In general, the attacks in WSNs can be classified as external attacks and internal attacks. In an external attack, the attacking node is not an authorized participant of the sensor network. Cryptography and other security methods can prevent some of external attacks. However, node compromise, the major and unique problem that leads to internal attacks, will eliminate all the efforts. Knowing the probability of node compromise will help systems to detect and defend against it. Although there are some ...