# A Security Assessment Mechanism for Software-Defined Networking-Based Mobile Networks
## 1 Introduction
There is already lots of research focusing on traditional network security assessment. In the earlier period, security assessment methods were only applicable to isolated components. However as multi-stage attacks have become the most harmful network security threats, these methods are not enough. The reason is that these methods did not consider the security holes introduced by the interconnections of local vulnerability [17]. To address the problem of security holes, attack graphs have been proposed as security assessment methods by building security models of network systems [17; 18; 19; 20; 21]. In the research of [PERSON] _et al._[22], attack graphs are used to model network vulnerabilities. Then they perform a risk analysis by a Bayesian method. The Bayesian method is also used to model potential attack paths in a system described by [PERSON] and [PERSON] in [23]. Based on the background knowledge of the attacker, including attack mechanism, they develop algorithms to compute attack paths. [PERSON] _et al._[24] use a Bayesian method to quantify the chances of network compromise. Moreover, they develop a security mitigation and management plan according to these results. However, none of them can be applied directly in SDN-MNs because they only focus on traditional networks and do not take the special properties of SDN-MNs into consideration. Firstly, these methods are only suitable for relatively static networks. They do not take the dynamic nature of SDN-MNs into consideration. Secondly, the traditional algorithms of attack graph generation are only suitable for relatively simple networks. When the network becomes more complex, the efficiency of these algorithms deceases greatly, so these traditional methods cannot deal with the diversity and complexity of SDN-MNs. Based on the aforementioned analysis, it is very necessary to have an effective security assessment mechanism for SDN-MNs considering their distinctive features. Firstly, a methodology to measure the total security level of SDN-MNs is needed. When SDN-MNs interconnect nodes in the network, local vulnerabilities will introduce new security holes because of this connectivity [17]. This methodology needs to not only deal with the security holes, but also deal with the diversity and complexity of SDN-MNs. Secondly, a way to quantify the influence caused by dynamic properties of SDN-MNs is important as well, so besides the methodology, what factors and how they influence SDN-MN security assessments must be taken into consideration. To address these problems, a security assessment scheme for SDN-MNs using attack graphs and an Analytic Hierarchy Process (AHP) is proposed. The rest of the paper is organized as follows: a background on mobile network architectures and SDN-MNs is introduced in Section 2. The structure of the proposed security assessment methodology is described in Section 3. Section 4 presents the details of the proposed attack graph model and the attack graph generation algorithm. The Node Minimal Effort (NME) attack graph quantification method considering the dynamic factors in SDN-MNs is discussed in Section 5. In Section 6, a case study is illustrated. Finally, we conclude the paper in Section 7.