Chapter 1 first introduces the basics of Internet of Things, discusses the fundamental concepts, architecture, key technologies, and applications of the IoT security, so that students can have a general understanding on the framework of IoT security. Chapter 2 presents the IoT threat model, allowing students to understand what threats IoT may face and how they differ from traditional threats. Chapter 3 is a transitional chapter and is the overarching chapter of the entire textbook, which first discusses the threat model presented in chapter 2, and then what are the basic technologies, overall foundational technologies and integrated framework technologies that we might adopt.