# 5G Security Threat Assessment in Real Networks
## 1 Introduction  
In February 2017, international telecommunication union (ITU) released a report that established key requirements which is minimum requirements related to technical performance for IMT-2020 for 5G mobile communication technology [1]. This report requested 1 GHz of minimum bandwidth, 20 Gbps of maximum data transmission rate, and 1 ms of the shortest latency time for next-generation services. These are technical requirements to realize the key purposes of 5G: super-connection, ultra-fast, and ultra-low latency, and also the minimal requirements to realize various 5G services. 5G mobile communication is more innovatively advanced compared to 4G mobile communication in general including speed, using protocol, and network configurations. 5G wireless network is configured in soft defined network (SDN) with 20 Gbps speed, 20 times faster than existing long term evolution (LTE), while the 5G core network has been changed from a centralized type to a decentralized type to minimize traffic transmission delay. Owing to such technical changes, ITU-R defined 5G services. It classified 5G services into enhanced mobile broadband (eMBB) where speed is a key element, massive machine type communication (mMTC) where bandwidth is a key element, and ultra-reliable and low latency communication (uRLLC) where latency time minimization is required, and configured the services to use 5G infrastructures in industrial environment throughout society [2]. 5G technical standards are led by 3 rd Generation Partnership Project (3 GPP), and release 15 frozen in March 2019 defines the architectures of non-standalone (NSA) and standalone (SA) and covers LTE system migration. In addition, release 16 frozen in July 2020 covers 5G-based convergence industry support including 5G-vehicle to everything communication (V2X) and 5G internet of things (IoT), along with performance improvements in 5G system. In release 17, which will be frozen in March of 2022, standardization is underway with the aim of expanding 5G coverage, transmitting small data, and utilizingunlicensed bands. Additionally, as sales of 5G-related industries are on the rise, sales of 5G wireless network infrastructures are expected to reach USD 6.8 billion in 2021 according to reports published by the Gartner as shown in Table 1[3]. In this context, the voices of users calling for a safe 5G service environment are growing, and many reviews are required before launching the services because of the possibility of inherent security threats in existing LTE communication network. Additionally, new 5G security threats need to be identified in advance due to technical changes differentiated from 4G, and service safety must be strengthened by developing security technology dedicated to 5G, if necessary. In addition, the scale of the global 5G security market is expected to grow at 50% of the compound annual growth rate (CAGR) to about USD 4 billion in 2023 and about USD 7 billion in 2025. In particular, more than 95% of the 5G security market is occupied by the field of security solutions [4]. Recently, serious security threats are being reported in papers such as [PERSON] et al. and [PERSON] et al. [5,6]. However, most mobile carriers (5G service operator) are providing 5G services without applying techniques of reaction related to security threats. The contribution of this paper is as follows and the main contribution is that we provide insight into what security challenges are valid in the real 5G NSA network and how they could be mitigated. * We divided 5G NSA security threats into radio access network (RAN) and core network (CN) to create an attack tree and develop 15 test cases that can be applied to real networks. * We verified the developed 15 test cases on the actual three mobile carriers' networks and identifies eight valid vulnerabilities. * Of these eight valid vulnerabilities, we proposed equipment PKG software patches or configuration changes for five and relevant countermeasures for the remaining three. The composition of this paper is as follows.