防火墙在传输网络中的吞吐量与管理问题及解决方案

讨论防火墙在大型传输网络(Transit Network )应用中的管理和吞吐量问题：一是手工方式配置分布在各个接入点的多个防火墙,无法适应开放的、动态的网络环境;二是大量的过滤规则导致防火墙吞吐量下降.针对大量防火墙的管理问题,该文提出了一种访问控制政策的自动分配与动态配置模型,将全局过滤规则自动地分发到相应的防火墙;同时利用入侵监测系统和搜索引擎的结果,自动定位防火墙、动态配置过滤规则,实时地过滤不良站点,终止攻击行为.针对单个防火墙的吞吐量问题,提出了一种基于散列表的规则匹配算法,该算法可以将时间复杂度从O(N)降低到O(1),从而大大提高防火墙的吞吐量.     

基于规则的防火墙匹配算法研究

传统防火墙包过滤过程是通过数据包与过滤规则顺序匹配,直到有一条规则匹配后即可停止。当过滤规则日益增多时,防火墙的吞吐量也不断下降,严重影响了网络的性能。该文提出并设计了快速的规则匹配算法,改变了以往的顺序匹配,极大地提高了防火墙的吞吐量和性能。     

基于区域分割的防火墙部署与配置

防火墙技术作为内部网络与外部网络之间的第一道安全屏障,是受到人们重视的网络安全技术之一。本文为提高网络安全的健壮性,从实施网络安全策略的角度,提出了一种以区域分割的三角方式部署防火墙系统的方案,说明了基于Cisco FIX525防火墙配置方法,以及访问控制列表与防火墙包过滤规则的联合应用方法。实用检验说明,这种方案能够较好地实现网络安全访问控制,有效地提高网络安全性。     

一种防火墙规则快速匹配方法

包过滤是防火墙的一项基本技术,一种快速的规则匹配方法,能极大地提高防火墙的吞吐量和性能。RFC算法是具有代表性的包分类算法,分类速度快。文章着眼于应用RFC算法提高防火墙访问控制列表（ACL）的搜索速度,对RFC算法的建立过程、算法的性能等作了简单介绍,对适合防火墙实际应用的RFC算法进行了阐述,并在防火墙上进行了测试验证。     

组合出入口访问控制的防火墙系统研究

针对军事网络特殊安全需求,提出了一种组合出人口访问控制的网络边界安全防护手段,在抗网络攻击方面,采用包过滤防火墙与基于神经网络和基于协议分析和规则匹配的入侵检测技术相结合的方法,提高入侵检测的准确性;在防信息泄密方面,在出口访问控制中引入身份认证机制及内容审查和过滤机制,可建立更灵活的安全审计和访问控制策略,有效阻截敏感或涉密信息外泄,实现对泄密源的有效跟踪。     

包过滤防火墙相关规则的排序及向无关规则的转化

提出了防火墙规则排序的算法 .防火墙进行包过滤时 ,规则集中的规则是顺序匹配的 ,这样防火墙过滤效率不高 .为了应用快速的非顺序的规则匹配算法 ,则必须将相关的防火墙规则转化为无关的规则 ,本文为此提出了防火墙相关规则向无关规则的转化算法 .两个算法实现之后的应用效果明显     

路由器访问控制列表在网络安全中的应用

访问控制列表（ACL）是解决和提高网络安全性的方法之一,是用来过滤与控制进出路由器数据流的一种访问控制技术,可以限制网络流量,提高网络性能,控制通信流量。文中探讨了访问控制列表的基本概念及工作原理,并列举了访问控制列表在网络安全方面的具体应用。结合配置实例,介绍如何在路由器下通过访问控制列表来构建计算机网络的防火墙体系结构,对局域网安全性能进行保护。在路由器下配置ACL,成为构建网络安全体系的一种技术手段。     

通过访问控制列表分析网络病毒入侵和恶意攻击

访问控制列表（Access conuol list,简称ACL）是解决和提高网络安全性的方法之一,是用来过滤与控制进出路由器数据流的一种访问控制技术,可以限制网络流量,提高网络性能,控制通信流量。本文探讨了访问控制列表的基本概念及工作原理,并列举了访问控制列表在网络安全方面的具体应用。结合配置实例,介绍如何在路由器下通过访问控制列表来构建计算机网络的防火墙体系结构,对局域网安全性能进行保护。在路由器下配置ACL,成为构建网络安全体系的一种技术手段。     

扩展访问控制列表在校园网中的应用

扩展访问控制列表是在三层交换机和路由器上经常采用的一种防火墙技术,它可以根据一定规则对经过该网络设备的数据包进行控制,主要起到流量过滤和保护网络的作用,常用于校园网络。本文从基本概念入手,深入剖析了扩展访问控制列表的工作过程和配置方法,对如何在校园网应用进行了全面的探索和研究。     

一种基于冲突检测的无关联规则集匹配算法

防火墙已经成为网络安全体系中一个关键的角色,对防火墙的管理越来越受到重视。本文针对在防火墙管理中容易出现的过滤规则冲突问题和规则匹配效率问题,提出了一种基于冲突检测的无关联规则集匹配算法。本文通过对规则进行分析,确定了规则库中的规则应该符合的五个关系;通过对冲突规则的分类,得到了按照各种冲突的特性进行冲突检测产生的状态图,有助于对防火墙的现有规则库进行重写优化。本文在分析传统的线性顺序规则匹配算法和树形规则匹配算法的基础上,提出一种基于冲突检测的无关联规则集匹配算法,其平均比较次数为O(lg(n)),性能上大大优于现有的算法。     

Firewall policy verification and troubleshooting

Firewalls are important elements of enterprise security and have been the most widely adopted technology for protecting private networks. The quality of protection provided by a firewall mainly depends on the quality of its policy (i.e., configuration). However, due to the lack of tools for verifying and troubleshooting firewall policies, most firewalls on the Internet have policy errors. A firewall policy can error either create security holes that will allow malicious traffic to sneak into a private network or block legitimate traffic disrupting normal traffic, which in turn could lead to diestrous consequences.We propose a firewall verification and troubleshooting tool in this paper. Our tool takes as input a firewall policy and a given property, then outputs whether the policy satisfies the property. Furthermore, in the case that a firewall policy does not satisfy the property, our tool outputs which rules cause the verification failure. This provides firewall administrators a basis for how to fix the policy errors.Despite of the importance of verifying firewall policies and finding troublesome rules, they have not been explored in previous work. Due to the complex nature of firewall policies, designing algorithms for such a verification and troubleshooting tool is challenging. In this paper, we designed and implemented a verification and troubleshooting algorithm using decision diagrams, and tested it on both real-life firewall policies and synthetic firewall policies of large sizes. The performance of the algorithm is sufficiently high that they can practically be used in the iterative process of firewall policy design, verification, and maintenance. The firewall policy troubleshooting algorithm proposed in this paper is not limited to firewalls. Rather, they can be potentially applied to other rule-based systems as well.     

Detection of firewall configuration errors with updatable tree

The fundamental goals of security policy are to allow uninterrupted access to the network resources for authenticated users and to deny access to unauthenticated users. For this purpose, firewalls are frequently deployed in every size network. However, bad configurations may cause serious security breaches and network vulnerabilities. In particular, conflicted filtering rules lead to block legitimate traffic and to accept unwanted packets. This fact troubles administrators who have to insert and delete filtering rules in a huge configuration file. We propose in this paper a quick method for managing a firewall configuration file. We represent the set of filtering rules by a firewall anomaly tree (FAT). Then, an administrator can update the FAT by inserting and deleting some filtering rules. The FAT modification automatically reveals emerged anomalies and helps the administrator to find the adequate position for a new added filtering rule. All the algorithms presented in the paper have been implemented, and computer experiments show the usefulness of updating the FAT data structure in order to quickly detect anomalies when dealing with a huge firewall configuration file.     

刍议计算机网络安全之防火墙

网络安全已成为人日益关心的问题,而网络防火墙是一种隔离控制技术,通过预定义的安全策略,对内外网通信强制实施访问控制,防火墙较常用的技术有应用网关、状态检测、包过滤等技术。在保护内部网络安全的前提下:其主要作用是在网络入口外检查网络通信,设定用户的安全规则,提供内部网络的安全,保障内外网络通信。     

On the use of open-source firewalls in ICS/SCADA systems

ABSTRACT

Firewalls are one of the most widely used security devices to protect a communications network. They help secure it by blocking unwanted traffic from entering or leaving the protected network. Several commercial vendors have extended their firewall capabilities to support SCADA protocols or designed SCADA-specific firewalls. Although open-source firewalls are used successfully in IT networks, their use in SCADA networks has not been properly investigated. In this research we investigate the major open-source firewalls for their use in SCADA networks and identify Linux iptables’ potential as an effective SCADA firewall. Iptables is a powerful open-source firewall solution available as part of most Linux distributions in use today. In general, use of iptables as a network-level firewall for SCADA systems has been limited to basic port and host filtering, without further inspection of control messages. We propose and demonstrate a novel methodology to use iptables as an effective firewall for SCADA systems. This is achieved by utilizing advanced iptables features that allow for dynamic inspection of packet data. It is noteworthy to mention that the proposed solution does not require any modification to the netfilter/iptables framework, making it possible to turn a Linux system into an effective SCADA firewall. The approach has been tested by defining filtering rules for the Modbus TCP protocol and validating its ability to defend against various attacks on the protocol.     

防火墙的动态访问控制机制

防火墙的静态过滤规则对安全的管理是基于IP地址而非基于用户,这在实际应用中是很不方便的。针对这种情况,文章提出了一个防火墙的动态访问控制机制,它可以在验证用户身份的基础上,实施基于用户的灵活的动态安全策略。该机制利用HTTP重定向技术实现透明的WEB认证,采用事件驱动方式、BitMap和Hash表算法等保证系统具有良好的性能。目前该机制的原型已经在Linux下实现,并应用在防火墙上,实践表明该机制具有安全策略灵活且可管理,使用简单,大用户量下扩展性好等优点。     

Improving cloud network security using the Tree-Rule firewall

This study proposes a new model of firewall called the ‘Tree-Rule Firewall’, which offers various benefits and is applicable for large networks such as ‘cloud’ networks. The recently available firewalls (i.e., Listed-Rule firewalls) have their limitations in performing the tasks and are inapplicable for working on some networks with huge firewall rule sizes. The Listed-Rule firewall is mathematically tested in this paper to prove that the firewall potentially causes conflict rules and redundant rules and hence leads to problematic network security systems and slow functional speed. To overcome these problems, we show the design and development of Tree-Rule firewall that does not create conflict rules and redundant rules. In a Tree-Rule firewall, the rule positioning is based on a tree structure instead of traditional rule listing. To manage firewall rules, we implement a Tree-Rule firewall on the Linux platform and test it on a regular network and under a cloud environment respectively to show its performance. It is demonstrated that the Tree-Rule firewall offers better network security and functional speed than the Listed-Rule firewall. Compared to the Listed-Rule firewall, rules of the Tree-Rule firewall are easier to be created, especially on a large network such as a cloud network.     

Optimization of parallel firewalls filtering rules

As filtering policies are getting larger and more complex, packet filtering at firewalls needs to keep low delays. New firewall architectures are needed to enforce security and meet the increasing demand for high-speed networks. Two main architectures exist for parallelization, data-parallel and function-parallel firewalls. In the first, packets are distributed across a set of identical firewalls that implement the entire policy. In the second, each firewall implements a subset of the policy with a fewer number of rules, but the packets have to be duplicated and processed by all the firewalls. This paper proposes a new architecture function-parallel with pre-processing that combines the advantages of both architectures. The proposed architecture has the advantage of not duplicating the data, so that the processing time can be significantly reduced. Moreover, our architecture enables stateful inspection of packets, which is necessary to prevent multiple types of attacks. The performances of this architecture have been proven to be scalable for large security policies.