Abstract: Wireless sensor networks (WSNs) are an important for monitoring distributed remote environments. As one of the key technologies involved in WSNs, nodes fault detection is indispensable in most WSN applications. It is well known that the distributed fault detection scheme checks out the failed nodes by exchanging data and mutually testing among neighbor nodes in this network., but the fault detection accuracy of a scheme would decrease rapidly when the number of neighbor nodes to be diagnosed is small and the node’s failure ratio is high. an improved scheme is proposed by defining new detection criteria. Simulation results demonstrate that the improved scheme performs well in the above situation and can increase the fault detection accuracy greatly. wireless sensor-actor networks, sensors probe their surroundings and forward their data to actor nodes. Actors collaboratively respond to achieve predefined application mission. Since actors have to coordinate their operation, it is necessary to maintain a strongly connected network topology at all times. Moreover, the length of the inter-actor communication paths maybe constrained to meet latency requirement. Distributed Actor Recovery Algorithm (DARA) Most existing works mainly focus on the design of the trust models and how these models can be used to defend against certain insider attacks. However, these studies are empirical with the implicit assumption that the trust models are secure and reliable. In this paper, we discuss several security vulnerabilities that watchdog and trust mechanisms have, examine how inside attackers can exploit these security holes, and finally propose defending approaches that can mitigate the weaknesses of trust mechanism. We observe that many existing trust models adopting watchdog as their monitoring mechanism do not explicitly address these weaknesses. Our goal in this paper is to demonstrate how serious insider attacks can be in WSNs.

Keywords: Network security, virtual network system computing, intrusion detection, attack graph, zombie detection.