This book presents methods for advancing green IoT sensor networks and IoT devices. Three main methods presented are: a standalone system to support IoT devices that is informed by the amount of energy the solar array system can produce; a model of securing a building's main power supply against unauthorized use; and security of the IoT devices and their networks. For each, the authors outline the methods, presents security and privacy issues, and their solutions. The work suggests a layered approach to expose security issues and challenges at each layer of the IoT architecture and proposes techniques used to mitigate these challenges. Finally, perspectives are drawn and discussed for future directions in securing IoT sensor networks, covering evolving areas such as artificial intelligence, blockchain technology, sensor Internet of People, context-aware sensing, cloud infrastructure, security and privacy, and the Internet of Everything.