With the rapid proliferation of Internet-of-Things (IoT) devices, understanding IoT security has become increasingly critical, especially in safeguarding hardware components that serve as the backbone of these systems. This chapter delves into the essential security requirements such as trust, privacy, and integrity, and investigates hardware vulnerabilities, including common attack vectors and encryption threats. It categorizes IoT architectures across various layers and examines real-world case studies, such as EV charging stations and medical devices, to highlight the practical implications of security breaches. Additionally, it compares IoT security policies across different countries, offering a global perspective on safeguarding these devices. This study organizes state-of-the-art research, making it easier to comprehend the interplay between security requirements, architectural vulnerabilities, and effective solutions, emphasizing the critical importance of securing IoT ecosystems.