Wireless Multimedia Sensor Networks (WMSNs) have drawn tremendous attention because of their potential impact on scientific research and their numerous attractive applications. However, security is one of the main challenges to WMSN. During the data transmission from source to destination, the intermediate nodes may misbehave as a malicious node. So, before reliable data transmission, these malicious nodes are to be detected. In this paper, Fuzzy logic system is presented for malicious node detection. Using this fuzzy system, the trust score is calculated for each sensor node in the network. Depend on the calculated trust score, malicious nodes are detected. For securable data transmission, Improved Elliptic Curve Cryptography (IECC) algorithm is presented. In ECC, Oppositional Particle Swarm Optimization (OPSO) is included for optimal key generation. Simulation results show that the performance of this proposed approach outperforms that of the existing approaches in terms of energy consumption, network lifetime and delay. © 2020 Elsevier B.V., All rights reserved.