Research On Risk Assessment Method Of Information Security In Communication-Based Train Control Systems

The integrated application of advanced communication and computer technology in rail transit has prompted the development of systematic,informative and inteligent train control system.At the same time,the information security risk of train control system has become more and more serious.At present,the information security analysis method of traditional IT and industrial control system cannot meet the need of information security analysis for train control system.Domestic and foreign researches on information security assessment technology of train control system are very few,and existing researches barely consider the characteristics of train control system security redundancy structure and "Fail-Safe".Therefore,it is very important to carry out the research on the security risk assessment method of train control system.Based on the above factors,this paper mainly studies the information security risk assessment technology of train control system.This is the first application of the Bayesian Attack Graph(BAG)as the risk assessment model in train control system.The nodes of BAG model are expanded to describe system characteristics more accurately.Then the goal of information security assessment of train control system is proposed.The risk of train control system itself and the information security event which is most likely to happen are analyzed.The specific research contents are as follows:(1)The current situation of industrial control system and train control system information security is researched.Communication-Based Train Control(CBTC)Systems based on Wireless Local Area Networks(WLANs)are taken as the research object.Information security risk assessment elements including assets,system vulnerabilities and sources of system threats are analysised.(2)The information security risk assessment technology based on Bayesian attack graph is studied.Firstly,typical risk assessment techniques are analyzed,and the Bayesian attack graph is selected as the information security assessment technique of CBTC systems.Then omitting subgraphs,graph clusters and detecting gates are introduced into the BAG nodes to apply to information security modeling of CBTC systems.At last,the BAG modeling steps are given.(3)The security event is proposed to analysis baysesian attack graph model.Firstly,CBTC minimal system is defined as the object of analysis,and BAG model is established.Secondly,the attack paths are extracted based on the established BAG model and are combined with form a security event.Then the risks of security events of CBTC systems are analyzed.Finally,the most likely security event of CBTC systems and the risk level of CBTC systems are analyzed.(4)The correctness of the Bayesian assessment results is verified.By analyzing the CBTC systems based on WLAN,Analytic Hierachy Process(AHP)model is constructed,and the risk of train control system is analysed by fuzzy theory.Finally,the correctness of evaluzaion risk level results of Bayesian attack graph model is verified.In this paper,the bayesian attack graph model can be used to correlate the vulnerabilities of the system,analyze the information security event which is most likely to happen,and carry out the risk assessment of the system.By the verification of AHP-fuzzy comprehensive evaluation method,the bayesian attack graph model presented in this paper can correctly reflect the systematic risk level of CBTC system.