The growing demand for mobile Internet, and the increasing number of connected devices, has required significant advancements in radio technology and networks compared to the previous generations of mobile telecommunication. Security however has only seen incremental changes to the previous mobile telecommunication generation, with enhancements that mitigate new threats and address revealed weaknesses. 5G is expected to change this, as novel use-cases will demand new trust models and require novel security solutions. In this paper, we examine the state of 5G Security, and start by describing the new expectations, requirements and enablers in 5G and the design principles conferred by material presented in selected publications. Furthermore, we describe the historic development of the authentication and key agreement protocols, which were introduced with GSM (2G), as an example of the incremental improvements to security. Additionally, we present select published papers that suggest different types of attacks on the current generations of mobile networks, and solutions to the identified weaknesses, which must be taken into account in 5G security. Finally, we describe a proposed 5G Security architecture, which bring new models for authentication, authorization and accounting (AAA) to 5G. The role of 5G security is clear, it must not only meet the basic security requirements in confidentiality, integrity and privacy, but also foster user confidence in mobile telecommunication.