Cryptographic mechanisms alone are insufficient to protect Wireless Sensor Networks (WSNs), because sensors are deployed for long periods in hostile environments where it is possible for an adversary to physically take over a sensor and obtain access to the cryptographic keys stored in the sensor’s internal memory. Thus, reputation-based trust systems are employed to detect abnormal activities and enhance the trustworthiness among sensors. Unfortunately, existing reputation-based trust systems for WSNs do not investigate the robustness against WSN-related or reputation-related attacks. This paper provides a comprehensive analysis for current reputation-based trust systems by surveying the current “state-of-the-art” work in this area.