Research On Cyber Security Risk Assessment Method Of CBTC Systems Oriented To Cloud Computing

At present,a number of cities in China have started to build rail transit cloud computing platform.The migration of Communication Based Train Control(CBTC)systems to cloud computing platform is the development trend of urban rail transit,but cyber security problem is one of the key obstacles to its further development.Risk assessment is the first scientific problem in the cyber security research of CBTC system cloud migration.In addition,the weak points of cyber security in the system can be effectively identified through risk assessment,which has important theoretical guiding significance for promoting cloud migration of CBTC systems.This paper summarizes the research status of cyber security risk assessment methods for industrial control systems,cloud computing and CBTC systems.Combining the characteristics of CBTC systems and cloud computing,we study the cyber security risk assessment method of CBTC systems oriented to cloud computing.The main work is as follows:(1)Identification of cyber security risk factors in CBTC System oriented to cloud computing.Firstly,the cyber security risk factors of CBTC systems and cloud computing are analyzed.Then,we research the mode of CBTC systems migration to cloud computing platform,as well as the cyber security vulnerabilities and threats after the migration.(2)Analysis of the probability and impact of attack events in CBTC Systems oriented to cloud computing.The complex network model of CBTC systems oriented to cloud computing is constructed,and the impact of attack events on network connectivity is analyzed based on fault tree.The complex network attack graph scenario of CBTC Systems oriented to cloud computing is constructed to analyze the attack path and the probability of attack events.The coupling relationship between cyber domain and physical domain of cloud computing oriented CBTC system is analyzed,and the influence of attack events on physical domain is analyzed.(3)Cyber security risk assessment method for CBTC systems oriented to cloud computing is proposed.The attack process is simulated based on reinforcement learning,and the risk value of each attack action is regarded as reward.The Q-learning algorithm is used to generate the optimal attack path in CBTC systems oriented to cloud computing,and the cumulative reward of the optimal attack path is taken as the risk value of the system.(4)A CBTC simulation system is migrated to the cloud computing platform,and the risk assessment method of CBTC systems oriented to cloud computing proposed in this paper is verified.Then,the risk level of cyber security before and after cloud migration of the CBTC simulation system is compared,and security protection strategies suitable for CBTC systems oriented to cloud computing are given.Experimental results show that the cyber security risk situation of CBTC systems after cloud migration will be more severe,but by taking comprehensive protective measures,the cyber security level can be significantly improved.