计算机网络脆弱性评估方法研究
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摘要
计算机的普及和通信技术的迅速发展,使计算机网络已经渗透到人们的日常生活中。随着用户的增长、需求的增加,计算机网络的规模和应用急剧扩张。计算机网络资源管理分散,用户普遍缺乏安全意识和有效的防护手段,各类软硬件产品和网络信息系统在规划、设计、开发、维护、配置、管理等各环节中普遍存在脆弱性,导致计算机网络面临着严峻的安全形势,已成为严重制约网络发展的因素之一。脆弱性评估技术通过综合分析计算机网络脆弱性的利用路径和可能性,对网络安全状况给出量化评估结果,为网络安全的优化提供依据。目前,计算机网络脆弱性评估已经成为信息安全领域的研究热点之一。
本文在对现有网络脆弱性评估方法调研分析的基础上,提出了一种基于网络脆弱性攻击图的脆弱性评估模型,通过对网络脆弱性攻击路径的概率分析和关键脆弱性的定位,给出网络安全状况的总体评价并明确影响网络安全的关键因素。本文的主要工作如下：
首先,给出了网络脆弱性评估的相关元素定义,并对构成网络的基本元素进行模型化表示,建立网络脆弱性评估模型框架。在此基础上,利用网络脆弱性评估元素的模型化参数作为输入,根据攻击信息中脆弱性利用之间的依赖关系,提出一种脆弱性攻击图生成方法。
其次,针对网络整体脆弱性的评估需求,采用贝叶斯网络对脆弱性攻击图进行分析。将脆弱性攻击图使用贝叶斯网络模型化表示,给出脆弱性攻击图的攻击概率精确推理过程,针对精确推理在处理复杂网络时的时间复杂度缺陷,提出一种基于随机数迭代采样的贝叶斯网络近似推理算法。通过对采样样本的分析统计,获得脆弱性攻击的近似概率。通过实验对精确推理和近似推理结果的比较,验证了近似推理算法的有效性和可行性。
最后,针对网络关键脆弱性的分析需求,提出了基于网络中心性理论的关键脆弱性分析方法。将网络中心性理论引入脆弱性攻击图分析,结合节点度与节点介数的分析方法,提出了节点修正介数的概念。通过节点的修正介数来量化评估攻击图中的关键脆弱性节点,为网络中脆弱性的修复和网络安全的优化提供依据。实验分析表明,这种方法克服了以往单一的网络中心性分析方法使用条件受限的弊端,评估结果更加合理可信。
网络脆弱性评估能够帮助我们明确目标系统存在的关键脆弱性以及各种存在的潜在攻击路径,并通过数学方法对其进行量化评判,指导我们在安全资源有限的情况下,如何选择有效的安全措施,以获取最大的安全回报,为提升网络安全状况提供参考依据。
The popularization of computers and the rapid development of communication technology make computer network can be found anywhere in people's daily-life. With the increasing number of users and requirements, the scale of computers and the applications are expanding extremely year by year. Because of the remediation of network resource management, the weakness of user's security consciousness, the lack of defense means, the vulnerabilities generally exist in various production phases of software、hardware and network information systems, such as planning, design, development, maintenance, configuration and management. Network is facing a critical security situation which has become one of the most severe factors to the network development. By analyzing the attack paths and the exploiting probabilities of vulnerabilities in networks, vulnerability assessment can show us the quantitative result of network security situation, and provide us the evidence for network security optimization. Nowadays, vulnerability assessment has become a hot topic in the field of network security.
On the basis of development and analysis of existing methods, this dissertation proposes a new network vulnerability assessment model based on vulnerability attack graph. By analyzing the probability of vulnerability exploitation paths and pointing out the key vulnerabilities, it can give us the overall evaluation of network security situation and indicate the most important factors which affect the network security. Our work in this dissertation is summarized as follows:
First, we define the elements of vulnerability assessment and model the network components, then build the vulnerability assessment model framework. Then we use the model of network components as input parameters, consider the relationship of vulnerabilities dependency and the exploiting path, and provide a method of the vulnerability attack graph(VAG) generation.
Then, according to the requirement of overall evaluation on network vulnerabilities, we analyze the VAG based on Bayesian network. We map the VAG into the Bayesian network and calculate the attack probability by using exact inference. According to the complexity for exact inference to the large-scale network, we propose a Bayesian-network-approximate-reasoning-based method for vulnerabilities assessment, this method makes the approximate reasoning to the VAG by stochastic sampling, then we can get the attack probability after the samples analysis and statistic. At last we plan an example to compare the result of exact inference with our approximate reasoning method to prove that our method is feasible and useful.
Lastly, according to the requirement of analyzing the key vulnerabilities in network, we propose a method on the key vulnerabilities analysis based on network centrality theory. We introduce the network centrality theory to analyze the VAG and propose a concept of corrected betweenness which combines betweenness with degree-theory to analysis the importance of the vulnerability nodes quantitatively in the attack graph. It will help us to find the key vulnerabilities which will have great effect on network security, then it will provide us the evidence to fix the vulnerability and enhance the network security. The experiment result shows that this method can overcome the drawbacks of the common centrality analysis methods, the evaluation result is reasonable and credible.
Network vulnerability assessment can help us locate the key vulnerability of target system and all potential attack paths. With the quantitative analysis by using the mathematic tools, it can guide us how to choose the effective security measure and get the maximum security return with limited security budget. Network vulnerability assessment can provide us efficient reference to improve network security situation.
本文在对现有网络脆弱性评估方法调研分析的基础上,提出了一种基于网络脆弱性攻击图的脆弱性评估模型,通过对网络脆弱性攻击路径的概率分析和关键脆弱性的定位,给出网络安全状况的总体评价并明确影响网络安全的关键因素。本文的主要工作如下：
首先,给出了网络脆弱性评估的相关元素定义,并对构成网络的基本元素进行模型化表示,建立网络脆弱性评估模型框架。在此基础上,利用网络脆弱性评估元素的模型化参数作为输入,根据攻击信息中脆弱性利用之间的依赖关系,提出一种脆弱性攻击图生成方法。
其次,针对网络整体脆弱性的评估需求,采用贝叶斯网络对脆弱性攻击图进行分析。将脆弱性攻击图使用贝叶斯网络模型化表示,给出脆弱性攻击图的攻击概率精确推理过程,针对精确推理在处理复杂网络时的时间复杂度缺陷,提出一种基于随机数迭代采样的贝叶斯网络近似推理算法。通过对采样样本的分析统计,获得脆弱性攻击的近似概率。通过实验对精确推理和近似推理结果的比较,验证了近似推理算法的有效性和可行性。
最后,针对网络关键脆弱性的分析需求,提出了基于网络中心性理论的关键脆弱性分析方法。将网络中心性理论引入脆弱性攻击图分析,结合节点度与节点介数的分析方法,提出了节点修正介数的概念。通过节点的修正介数来量化评估攻击图中的关键脆弱性节点,为网络中脆弱性的修复和网络安全的优化提供依据。实验分析表明,这种方法克服了以往单一的网络中心性分析方法使用条件受限的弊端,评估结果更加合理可信。
网络脆弱性评估能够帮助我们明确目标系统存在的关键脆弱性以及各种存在的潜在攻击路径,并通过数学方法对其进行量化评判,指导我们在安全资源有限的情况下,如何选择有效的安全措施,以获取最大的安全回报,为提升网络安全状况提供参考依据。
The popularization of computers and the rapid development of communication technology make computer network can be found anywhere in people's daily-life. With the increasing number of users and requirements, the scale of computers and the applications are expanding extremely year by year. Because of the remediation of network resource management, the weakness of user's security consciousness, the lack of defense means, the vulnerabilities generally exist in various production phases of software、hardware and network information systems, such as planning, design, development, maintenance, configuration and management. Network is facing a critical security situation which has become one of the most severe factors to the network development. By analyzing the attack paths and the exploiting probabilities of vulnerabilities in networks, vulnerability assessment can show us the quantitative result of network security situation, and provide us the evidence for network security optimization. Nowadays, vulnerability assessment has become a hot topic in the field of network security.
On the basis of development and analysis of existing methods, this dissertation proposes a new network vulnerability assessment model based on vulnerability attack graph. By analyzing the probability of vulnerability exploitation paths and pointing out the key vulnerabilities, it can give us the overall evaluation of network security situation and indicate the most important factors which affect the network security. Our work in this dissertation is summarized as follows:
First, we define the elements of vulnerability assessment and model the network components, then build the vulnerability assessment model framework. Then we use the model of network components as input parameters, consider the relationship of vulnerabilities dependency and the exploiting path, and provide a method of the vulnerability attack graph(VAG) generation.
Then, according to the requirement of overall evaluation on network vulnerabilities, we analyze the VAG based on Bayesian network. We map the VAG into the Bayesian network and calculate the attack probability by using exact inference. According to the complexity for exact inference to the large-scale network, we propose a Bayesian-network-approximate-reasoning-based method for vulnerabilities assessment, this method makes the approximate reasoning to the VAG by stochastic sampling, then we can get the attack probability after the samples analysis and statistic. At last we plan an example to compare the result of exact inference with our approximate reasoning method to prove that our method is feasible and useful.
Lastly, according to the requirement of analyzing the key vulnerabilities in network, we propose a method on the key vulnerabilities analysis based on network centrality theory. We introduce the network centrality theory to analyze the VAG and propose a concept of corrected betweenness which combines betweenness with degree-theory to analysis the importance of the vulnerability nodes quantitatively in the attack graph. It will help us to find the key vulnerabilities which will have great effect on network security, then it will provide us the evidence to fix the vulnerability and enhance the network security. The experiment result shows that this method can overcome the drawbacks of the common centrality analysis methods, the evaluation result is reasonable and credible.
Network vulnerability assessment can help us locate the key vulnerability of target system and all potential attack paths. With the quantitative analysis by using the mathematic tools, it can guide us how to choose the effective security measure and get the maximum security return with limited security budget. Network vulnerability assessment can provide us efficient reference to improve network security situation.
引文
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