Worldwide interoperability for microwave access (WiMAX), designed by the IEEE 802.16 standards group, is one of the most promising broadband wireless technologies with respect to delivering high-speed connectivity in the last mile. A mesh network configuration was added for improved coverage and throughput. We describe security concerns for WiMAX mesh mode such as malicious sponsor nodes and privacy. We also seek to reduce the processing load as a result of the use of link encryption. We introduce two different types of attacks as a result of different types of malicious sponsor nodes. The first type of attack occurs when the malicious sponsor node has not actually joined the current mesh network but solicits new nodes to join the mesh network through it. The second type of attack occurs when the malicious node is a member of the mesh network and selectively drops data from its child nodes. To prevent the first attack, we propose a new security protocol that adds to the standard control messages a pair of secret authorization keys (AK). To handle the second attack, we propose a reputation-based scheme that is specific to WiMAX mesh networks. We conduct a numerical analysis and simulations to highlight the strengths of the proposed schemes. The proposed reputation-based scheme uses the MSH-NCFG control message that is used in the WiMAX standard to send reputation information about nodes in the mesh network. Nodes that are joining the mesh network receive and process MSH-NCFG messages and decide which sponsor node through which to join the network. We conduct a numerical analysis to determine the amount of time for reputation information to propagate through the mesh network, thus allowing joining nodes to avoid malicious sponsor nodes. The simulation results show that the proposed scheme can reduce the overall data drop rate in WiMAX mesh networks in the presence of the aforementioned attacks from malicious sponsor nodes. Copyright © 2009 John Wiley & Sons, Ltd.