# A Systematic Survey on 5G and 6G Security Considerations, Challenges, Trends, and Research Areas
## 3 5G Security Architecture: A Systematic Approach
### Core Network
#### 3.1.3 SDN, NFV, MEC  
Software-Defined Networks (SDNs) and Network Function Virtualization (NFV) are the two dominant factors contributing to the successful rollout of 5G. SDN and NFV have allowed for the use of off-the-shelf networking equipment compared to previous generations of cellular communications needing to be supported with specific hardware. However, with this drastic change in the architecture, there are bound to be security concerns. 5G back-end networks are easier to operate and more centralized now than in the past, which greatly eases the burden on operators and system administrators. It also reduces the number of possible attack vectors. One concern, however, resulting from increased integration and reliance on software-controlled systems is discussed in [28]. The author states that Denial-of-Service (DOS) attacks may be more potent due to this centralized infrastructure. In some cases, if the system is overloaded, this could cause entire network components to fail. It is also mentioned that the integration of NFV into 5G raises some of its own concerns: NFV opens the door for failures in provisioning and securing the host systems of the virtualized network functions, thereby potentially exposing the utilized hypervisors to an attacker. If the hypervisor is left vulnerable due to a misconfiguration, the entire core network is at a very high risk of being compromised. Proper configuration of the NFV platform is also important to guard against cross-contamination of shared resources [29]. The author also shares that if there is a vulnerability in a virtualized core network function, malware could be used to gain access to information from other network users and potentially allow for unauthorized API calls. Unwarranted connections to a core network can be denied if a ZTA is utilized with mutual authentication and constant network monitoring. Software-Defined Networks have rapidly grown in popularity over the years, since they allow administrators to dynamically adapt their networks through intelligent softwarecontrols. This can be seen with most all of the papers presented in Table 2 substantially cover SDN, whereas blockchain and ZTA are less mentioned, as they are newer concepts. SDN further eases the burden of implementing security models for different applications within the network's control plane. This software-centric and programmatic approach to networking differs drastically from the historical--more physical and static--view of a network, as it incorporates many operations of an administrator's workflow into one central control system, thereby creating a cohesive network management interface. In SDN, the network comprises three layers: Application, Control, and Data. With this architecture, 5G operators are able to segment their network into different priorities, creating a market for providing different services to consumers. As SDN is a newer concept, the security of this system architecture may not be as robust as other more established systems. A survey conducted on SDN security [30] shares a few security analyses of Software-Defined Networks. One analysis shows that the popular OpenFlow protocol used in SDN can be susceptible to information disclosure and DoS attacks [31]. It is mentioned in the survey that methods to prevent these attacks may exist but are not proven in the text in a wide array of tests. The OpenFlow documentation advised the use of TLS with mutual authentication for devices on the network but did not specify the use of a specific version of TLS. The authors of the survey text also point out that different vendors' equipment may not support this security, causing more concern and the need for a more cohesive and standard approach to SDN. The paper mentions the need for more proposals in the advancements in the design of SDNs. One holistic approach presented is FRESCO [32], which allows for more rapid development of security modules that can be implemented as Open Flow modules.