## 3 Mobile Network Security Evolution and the Evolution of Threat Landscape
### Fifth-Generation Network Security  
With the advent of 5G telecommunications technology, there is an expanding proliferation of data transmission across vast digital landscapes. This significant shift in the realm of digital communications underscores the primacy of security in these next-generation networks. Security, in the context of 5G, encompasses multiple dimensions, from the privacy of personal information to the reliability and integrity of services offered through the network [51]. These elements have been a focal point in traditional networks; however, their importance is massively elevated in the 5G framework due to the inherent technical advancements and the larger, more diverse user-base that this technology caters to [52]. Fifth-generation networks, compared to their predecessors, are designed to handle a much broader range of applications, many of which involve the transmission of sensitive data and the delivery of critical services. Applications such as telemedicine, autonomous vehicles, and smart cities heavily rely on 5G networks for their operation, thereby escalating the need for robust and reliable security measures [53]. A summary of 5G security challenges is shown in Figure 5.  
Figure 4: Evolution from 1G to 5G. Figure 5: Fifth-generation architecture diagram. Furthermore, the envisaged increase in machine-to-machine communications in the 5G era implies a shift in the nature of information being transmitted, with increased volumes of sensitive, operational data being communicated across networks [54]. The broadening of the attack surface, due to the increasing complexity of the network and the sheer number of connected devices, adds another layer of intricacy to the security landscape in 5G. The highly distributed architecture of 5G, combined with the heterogeneity of devices and services it supports, create multiple potential points of vulnerability that could be exploited by malicious entities. Ensuring the security of 5G networks, therefore, calls for a multifaceted approach that addresses not only the encryption and protection of data but also the secure management and authentication of devices and users [55]. The evolution towards the more connected world that 5G represents is closely intertwined with the need for more comprehensive and sophisticated security measures. Table 2 reports the most pressing security challenges encountered in the 5G landscape. Each challenge is corroborated by the pertinent literature, thereby providing a multifaceted understanding essential for both researchers and practitioners in the field. The table encapsulates areas such as network slicing vulnerabilities, authentication weaknesses, data privacy concerns, security issues in mMTC, edge computing security risks, man-in-the-middle attacks, and SDN risks. Throughout the historical evolution of mobile networks, various strategies for securing these networks have been trialed, some proving to be more effective than others. The evaluation of these strategies offers valuable insights into the successful elements of security measures, as well as potential pitfalls to be avoided in the future. One of the significant successful strategies that have proven their effectiveness over time is the use of encryption. This is a measure that has been utilized since the advent of 2G networks, which transitioned from analog to digital data, thus increasing the risks of data interception and tampering. This led to the deployment of encryption algorithms, which have progressively become more sophisticated and robust as technology evolved from 2G to 4G [46; 49]. Consequently, in 4G networks, advanced encryption standards were implemented, providing a significant level of protection for data. Another successful strategy has been the incorporation of mutual authentication between the user and the network. This strategy emerged in the 3G era and was carried over into 4G networks. Mutual authentication ensures that both the user and the network are legitimate, reducing the risk of unauthorized access and impersonation attacks.