With the advancement of wireless communication technologies, it is now common for ordinary users to carry around mobile devices and perform various computing tasks on the road. Today, computers control every inch of equipment that once did not have a built-in computer. A variety of products, such as home appliances and connected cars, have computers embedded in them and are designed to function by constantly exchanging data with the cloud using wireless communication capabilities. They contain a large amount of storage capacity, various sensors and actuators, and implement a wide variety of functions. Various vulnerabilities are discovered every day in these products, and accordingly, various damages are expected to occur if these devices are hijacked by malicious users. This is potentially a major social threat. This Special Issue aims at addressing the topics on security in wireless communication systems across multiple levels, ranging from hardware, interfaces, protocols, applications and services to improve security, trust, and privacy in smart sensors, IoT devices, wearable devices, smart appliances, connected cars, 5G-connected infrastructure, and so on.