A network of drones or Unmanned Aerial Vehicles (UAVs) forms the Internet of Drones (IoD), enabling coordinated operations and data sharing for applications such as surveillance, delivery, and environmental monitoring. With the increasing integration of drones into daily life, ensuring their security becomes a major concern. The security of IoD is multifaceted, encompassing numerous strategies to protect against unauthorized access and control. Among these, two of the most pressing challenges are the development of effective authentication mechanisms and robust GPS spoofing detection and mitigation techniques. Authentication is essential for ensuring that only authorized drones can access and operate within the IoD network, preventing misuse and malicious activities that could compromise the system’s integrity. Equally important is GPS spoofing detection and mitigation, as UAVs heavily rely on GPS for navigation, and any interference can result in misdirection, causing accidents or mission failures. This chapter provides a comprehensive literature survey, examining the progression of authentication methods and GPS spoofing detection and mitigation mechanisms in IoD. The survey covers a range of strategies, from traditional signal analysis to cutting-edge AI-based solutions. It highlights recent advancements and identifies ongoing challenges, proposing future research directions to address these critical issues.