Defending Malicious Collision Attacks in Wireless Sensor Networks

Security is an important issue for sensor networks deployed in hostile environments, such as military battlefields. The low cost requirement precludes the use of tamper resistant hardware on tiny sensor nodes. Hence, sensor nodes deployed in open areas can be compromised and used to carry out various attacks on the network. In this paper, we consider the collision attack that can be easily launched by a compromised (or hostile) node: a compromised node does not follow the medium access control protocol and cause collisions with neighbor transmissions by sending a short noise packet. This attack does not consume much energy of the attacker but can cause a lot of disruptions to the network operation. Due to the wireless broadcast nature, it is not trivial to identify the attacker. In this paper, we propose a distributed scheme that is based on low-cost hardware and can effectively identify the source of a collision attack. Our scheme is based on analyzing physical-layer Received Signal Strength Index (RSSI) readings. We show that correct identification of an adversarial node can be achieved with greater than 85% accuracy. We further present a technique that degrades gracefully as the background noise increases.