Collaborative spectrum sensing in cognitive radio network (CRN) helps in increasing the accuracy of detection of the incumbent signal. Each node in an infrastructure-based CRN sends its local sensing report to the fusion center (FC), which aggregates the reports to arrive at a final sensing decision. However, collaborative sensing is vulnerable to the Byzantine attack (also known as spectrum sensing data falsification attack) in which malicious nodes falsify sensing reports in order to adversely affect the final sensing decision. Temporal data collected at the FC in the form of the sensing reports form a rich audit data set, which can be analyzed to identify malicious nodes, if any. In this paper, we present two anomaly detection techniques based on such an analysis. First, we exploit the frequency property of such statistical data and develop a lightweight intrusion detection scheme. Second, we use the Markov chain model which is based on the ordering property of the data to develop another intrusion detection scheme. Simulation results along with theoretical analysis show the validity of the two schemes.
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