Lejun Zhang

A Quantitative Evaluation Model for Network Security

The existing network security assessment models have the problems of inadequate capacity of quantitative analysis and lacking for vulnerabilities correlation. To address these problems, a hierarchical network security evaluation model is proposed. The network is divided into vulnerability level, service level, equipment level and network level. The model uses attack graph to correlate the network vulnerabilities, and then calculates the probabilities of successfully exploiting the vulnerabilities. On this basis, the quantitative risks of each level are calculated. Since this model much more accords with the features of network structure, it is an effectively guidance for the network administrators to develop and improve the network security policies.Chord is a kind of structured P2P networkbut the routing table in Chord suffers serious information redundancy and it is not very efficient. Therefore, a routing model and algorithm implementation for Chord based on layer-dividing(L-Chord) is proposed. Simulation experiments show that L-Chord compress- es the routing table length of most nodes into only one so as to eliminate repetitious entries and reduce the average lookup path length.L-Chord coordinates loo- kup efficiency and routing table length well.

A Survivability Quantitative Analysis Model for Network System Based on Attack Graph

Survivability is the ability of a system to continue operating despite the presence of abnormal events such as intrusions. Ensuring system survivability has increased in importance as critical infrastructures have become heavily dependent on computers. In this paper we present a survivability quantitative analysis model for network system based on attack graph, which indicates that survivability depends on network system itself, as well as the environment where its running. We identify the intrusion scenarios via attack graph analysis, and then suggest a quantitative measure of network system survivability. Mathematics formulas are given and network nodes that influenced survivability are investigated. From a case study, we identify the compromisable nodes that can be penetrated and damaged by intrusion and provide valuable suggestions to enhance system survivability design. The model is not only suitable for simple network systems but also applicable to distributed ones as long as the system is divided into atomic components.

A Survivability Information System Based on Service Self-Organization

A survivability information system based on service self-organization is proposed under the precondition of modules redundancy backup. The service self-organization way divides the system into services communications modules, services distribution modules, data storage modules according to service processing flow, the backup modules send its survivability information to the working modules duly, and get the latest service states list. When a module has the highest survivability, the system will do the service self-organization through different connection handoff techniques according to the functions of the modules and their location in system architecture. The validity of the survivability calculation method is proved by the simulation experiment. Examination proved that the method proposed in this paper can enhance the service survivability both of the steady state and instantaneous state by setting up a Web server in the network environment.

A Null Value Estimation Method Based on Similarity Predictions in Rough Sets

In this paper, we utilize rough set theory as a tool to deal with the problem of null-value estimation in an incomplete information system, a rating mechanism in collaborative filtering technology is introduced into this paper for the weakness of null value estimation based on similar relational algorithm (SIM-EM), such as no sparse degree process and low accuracy, and an improved null value estimation method, which based on SIM-EM is proposed from the perspective of similarity. The null value data is predicted and filled through the similarity of objects, otherwise a dual feature weight method is proposed according to the attributes feature in rough set, which improves the accuracy in similarity calculation, the improved algorithm is good at dealing with sparse rough set, and the accuracy and the mean absolute error is better than the original method.

A Novel Security Network Storage System Based on Internet

A novel security network storage system based on internet is put forward in this paper. First, the hierarchical model is presented consists of storage client, storage middleware and storage network. Second, two key technologies are proposed in detail including ISCSI protocol and distributed storage network; last experimental results prove that the system can improve the security of network storage effectively while not affecting the read and write speed.

Research on Disaster Tolerance System Based on Network Dataflow

In recent years, the disaster tolerance capability of network information systems has become the focus of research interest. In this paper, a disaster tolerance system architecture based on network dataflow is proposed and several techniques have been studied, namely, the rapid dataflow capturing, the failure packet filtering, the packet sequential storage technique supporting rapid retrieval, and the dataflow replay key technique supporting any revisit point. The disaster tolerance system using data streaming method does not incur extra system overhead, and is independent of specific applications. It can improve the data disaster tolerance generality and reduce deployment costs.

A method to enhance service survivability based on autonomous configuration

This paper puts forward the conception of service survivability and proposes an algorithm to enhance essential service survivability by autonomous configuration. This algorithm considers that survivability is the most important element of atomic module fulfilling essential service instead of failure rate. The contrast experiment validated the survivability computing method and the simulation confirmed that the autonomous configuration algorithm can efficiently enhance the survivability of essential service.