Nowadays, multi-radio multi-channel wireless mesh networks have been widely exploited to provide high-speed Internet access. By assigning different channels, the interference between wireless mesh network nodes can be greatly reduced, leading to a better network performance. However, the channel assignment attacks have imposed a serious security problem, where the diverse messages, that is, Channel Usage Message (CUM), Channel Change Message (CCM), Channel Switch Operation (CSO) and Security Alarm Message (SAM), are often used to launch attacks by the malicious nodes in order to disturb the normal channel assignment and thus the overall network performance. In this paper, we propose a joint anti-attack scheme (JAS) against the channel assignment attacks. Our JAS is composed of four key components: CUM, CCM, CSO and SAM defense schemes to protect the channel assignment. The CUM defense scheme verifies the CUM messages and their sender. The CCM defense scheme employs three rounds of CCM verifications. Furthermore, three control messages are exploited by the CSO defense scheme. The SAM defense scheme offers two rounds of verification for the alarm messages. Moreover, we apply our JAS to a popular distributed channel assignment algorithm, that is, Hyacinth. Through extensive simulation, the performance of the proposed scheme is evaluated by comparing with SeCA and SmartC in terms of Goodput and additional overhead. Observed from the simulation results, our scheme is demonstrated to outperform the best-known secure channel assignment algorithms.