对一种DoS攻击的分析及防范策略研究

Web服务器常常遭到来自外部网络主机的拒绝服务攻击,其中,SYN flood攻击是最常见的一种。攻击者使用伪造的源地址向服务器发送大量的TCP连接请求,致使服务器为每一个连接请求分配资源直至资源耗尽,因此,合法用户的正常访问也因为无法建立TCP连接而被拒绝。分析了SYN flood攻击的基本原理,对现有的几种处理资源耗尽及伪造源地址的方法进行了分析,指出了它们的优缺点。     

SPP: An anti-phishing single password protocol

Most users have multiple accounts on the Internet where each account is protected by a password. To avoid the headache in remembering and managing a long list of different and unrelated passwords, most users simply use the same password for multiple accounts. Unfortunately, the predominant HTTP basic authentication protocol (even over SSL) makes this common practice remarkably dangerous: an attacker can effectively steal users’ passwords for high-security servers (such as an online banking website) by setting up a malicious server or breaking into a low-security server (such as a high-school alumni website). Furthermore, the HTTP basic authentication protocol is vulnerable to phishing attacks because a client needs to reveal his password to the server that the client wants to login.In this paper, we propose a protocol that allows a client to securely use a single password across multiple servers, and also prevents phishing attacks. Our protocol achieves client authentication without the client revealing his password to the server at any point. Therefore, a compromised server cannot steal a client’s password and replay it to another server.Our protocol is simple, secure, efficient and user-friendly. In terms of simplicity, it only involves three messages. In terms of security, the protocol is secure against the attacks that have been discovered so far including the ones that are difficult to defend, such as the malicious server attacks described above and the recent phishing attacks. Essentially our protocol is an anti-phishing password protocol. In terms of efficiency, each run of our protocol only involves a total of four computations of a one-way hash function. In terms of usability, the protocol requires a user to remember only one password consisting of eight (or more) random characters, and this password can be used for all of his accounts.     

一种轻量级的动态化密钥协商的物联网身份认证协议研究

针对物联网络在用户身份验证上存在的安全性问题,提出一种轻量级的动态化密钥协商的物联网身份认证协议(DLT)。该协议在用户进行登陆验证上使用了时间戳值,这使得恶意攻击者不能使用早期的消息,可以防范重放攻击以及拒绝服务攻击;在认证和密钥协商阶段采用了用户、服务器、控制服务器三者之间的互相验证,并且在公共信道上对服务器密钥和随机值进行了分离处理,使得攻击者无法窃听到其他用户的安全信息。协议安全性分析及仿真对比结果表明,DLT协议相比对比协议具有更多的安全功能,可以防范多种网络攻击,并且协议的能量代价更低。     

一种更安全的基于智能卡的多服务器身份认证方案研究

随着网络和通讯技术的发展,多服务器的身份认证问题成为近几年研究的重点。针对Chuang等人提出的基于生物特征的多服务器密钥认证方案存在的安全性不足等问题,Wang等人进行了改进,但是仍未解决不同服务器密钥相同造成的恶意攻击和伪造攻击等问题。因此,本文提出了一种更安全的基于智能卡的多服务器身份认证方案。该方案在服务器注册阶段,将高熵秘密数与服务器的ID进行计算再重新分配给服务器,使得不同的服务器具有不同的密钥。最后通过五个方案功能和性能比较分析,得出改进方案比前三种方案时间上分别缩短了16.67%、20%、28.57%,且能有效阻止恶意服务器攻击、伪造攻击、重放攻击和中间人攻击等多种攻击,安全性得到了提高,满足实际网络的高可靠性需求。     

抵抗恶意服务器的口令增强加密方案

口令增强加密是一个近年来新出现的原语,可以通过增加一个第三方密码服务提供商承担辅助解密的功能,抵抗已有的服务器猜测低熵口令即可解密带来的恶意离线攻击风险,即实现了对口令认证进行增强并增加加密的功能.结合近年来新出现的算法替换攻击威胁,对提出该原语工作中的方案给出了一种服务器积极攻击的方法,该攻击具有不可检测性且可以让服务器仍然能实施离线攻击,从而证明原方案不具备其声称的抵抗恶意服务器的功能.接着讨论与总结能够抵抗恶意服务器实施算法替换攻击的方案应当具备的性质与构造特点;随后,给出一个能够真正抵抗恶意服务器算法替换攻击的方案并给出了仿真结果;最后,对于复杂交互式协议受到算法替换攻击时的安全性影响需要的系统性研究进行了展望.     

A comprehensive study of queue management as a DoS counter-measure

The purpose of a denial of service (DoS) attack is to render a network service unavailable for legitimate users. We address the problem of DoS attacks on connection-oriented protocols where the attacker tries to deplete the server connection by initiating communication with the server and then abandoning the communication. The most exploited attack in this category is the SYN-flood attack but other attacks using the same approach in stateful communication protocols also fall into this category. Our goals are twofold: first, to develop a mathematical model allowing us to analyse the trade-off between the attacker and the defender resources and second, to offer prevention mechanisms that can be used to defend against this category of attacks. We model the server queue of connections using Markov chains to establish a relationship between the server capacity, the attack rate and the impact on the service level. We analyse two methods of adjusting the timeout, threshold and linear, and we couple them with three policies of assigning the timeout to connections: the deterministic policy, the deferred policy and the utopian Poisson policy. First, theoretical modelling confirms that for any given strategy, there exists a linear trade-off between attack rate and targeted server queue size. However, the ratio that needs to be kept between them in order to maintain a similar level of quality of service differs between strategies; in that sense some are better than others. In particular, theoretical modelling also indicates that the linear deferred timeout strategy is very similar in performance to the linear Poisson timeout strategy, which in turn outperforms all the other dynamic timeout strategies. The dynamic timeout strategies always outperform the classical fixed timeout method. Our model is very general and can be used to capture the behaviour of the server queue during connection depletion attacks at various levels in the TCP protocol stack. We confirm the theoretical findings using stochastic simulations and network experiments of SYN-flood attacks. We also show how the model can be used when analysing a TCP connection establishment flood or a ticket reservation flood. The protection strategies we suggest are robust to changes in the attack model and our implementation is very efficient and transparent with respect to the server and applications it tries to protect. The strategies could therefore be easily integrated into existing operating systems and applications, or implemented in separate network devices.     

A new provably secure authentication and key agreement protocol for SIP using ECC

SIP has been chosen as the protocol for multimedia application in 3G mobile networks. The authentication mechanism proposed in SIP specification is HTTP digest based authentication, which allows malicious parties to impersonate other parties or to charge calls to others, furthermore, other security problems, such as off-line password guessing attacks and server spoofing, are also needed to be solved. This paper proposes a new authenticated key exchange protocol NAKE, which can solve the existing problems in the original proposal. The NAKE protocol is probably secure in CK security model, thus it inherits the corresponding security attributes in CK security model.     

基于网络的产品在线检测系统

基于TCP/IP协议,利用Socket易于客户/服务器模式(C/S)网络编程的功能,实现了客户端和服务器端之间的相互通信,并将其应用于浮法玻璃质量在线检测系统;同时提出一种自诊断方法,使得客户端可以自动检测Socket连接状态并在断开的情况下实现向服务器端的重连。     

Defense against SYN flooding attacks: A particle swarm optimization approach

SYN flooding attack is a threat that has been designed based on vulnerabilities of the connection establishment phase of the TCP protocol. In this attack some sources send a large number of TCP SYN segments, without completing the third handshake step to quickly exhaust connection resources of the victim server. Hence, a main part of the server’s buffer space is allocated to the attack half open connections and incoming new connection requests will be blocked. This paper proposes a novel framework, in which, the defense issue is formulated as an optimization problem. Then it employs the particle swarm optimization (PSO) algorithm to solve this optimization problem. Our theoretical analysis and packet-level simulations in ns-2 environment show that the proposed defense strategy called PSO_SYN decreases the number of blocked TCP connection requests and cuts down share of attack connections from the buffer space.     

在路由器上用SYN Cookie实现SYN Flood的防御

SYN Flood是目前流行的DDOS攻击手段,能够极为有效地攻击网站服务器,使得服务器资源耗尽而无法提供正常服务.由于利用了TCP/IP的协议漏洞,很难从根本上进行防范.给出一种在路由器上利用SYN Cookie机制实现对SYN Flood的防御,能够有效地保护服务器不受SYN Flood攻击,同时不会增加路由器的负担.     

MI_TCP--一种基于多映像的TCP连接容错策略

对运行于其上的服务进行容错是当今服务器必须具有的一种功能,TCP连接容错是实现这个功能的关键技术．为此,提出了一种基于多个连接映像的TCP连接容错策略(MLTCP),该策略并不需要对TCP连接状态进行备份,而是使每个TCP连接都存在多个同步的TCP连接映像．此策略无需修改客户端的用户程序和服务器端的服务程序;故障对客户端完全透明,即客户端程序感觉不到TCP连接的出错;当一台服务器上的TCP连接出错时,另一台服务器能真正做到无缝接管;并且在保证容错的前提下,尽量减少对系统性能的影响．     

遥测站采用HTTP协议传输图片的应用研究

针对遥测站采用水利行业规约传输图片效率较低等问题,为在水文自动测报系统中基于移动通信网络或者有线嵌入式以太网灵活、高效地传输图片,介绍遥测站的数据特点、拍摄图片的常用压缩格式和传输方式,研究在遥测终端机中应用HTTP协议传输图片的过程.采用HTTP协议,将遥测终端机作为客户端与服务器建立起TCP连接,应用层按照HTTP...     

一种基于无状态连接请求验证的SYN湮没攻击防御方法

已有SYN湮没攻击检测防御技术存在一个共性缺陷，就是在验证连接请求有效前分配一定的系统资源保存连接状态，基于无状态连接请求验证的方法可以有效地解决这一问题，但已有的方法存在验证有效后无法完整建立TCP连接、通讯双方状态不一致等问题．本文提出一种新的基于无状态连接请求验证的网关级SYN湮没攻击防御方法，该方法在解决已有问题并兼容现有TCP／IP协议栈实现的基础上，可实现对不同操作系统SYN湮没攻击的有效防御．     

一种抗恶意攻击的RFID双向认证协议

针对现有无线射频识别（RFID）认证机制存在的安全缺陷,提出一种新型抗恶意攻击的RFID双向认证协议,并基于GNY逻辑给出了协议的安全性证明。该协议将公钥加密算法和对称密钥加密算法相结合,采用阅读器双重认证及预认证阶段刷新密钥的方法,通过在标签中添加保护密钥同步的恶意攻击标记Tm,解决了当前协议中存在的认证效率较低,标签密钥更新失败导致位置跟踪和非法更新标签/服务器内部密钥造成拒绝服务（DoS）等问题,可抵抗重传,标签/阅读器假冒,通信量分析和去同步化等多种恶意攻击。分析结果表明：该协议具有安全性好,效率高,计算复杂度低等特点,适合于标签的大规模应用。     

PSO-SFDD: Defense against SYN flooding DoS attacks by employing PSO algorithm

A DoS attack can be regarded as an attempt of attackers to prevent legal users from gaining a normal network service. The TCP connection management protocol sets a position for a classic DoS attack, namely, the SYN flood attack. In this attack some sources send a large number of TCP SYN segments, without completing the third handshake step to quickly exhaust connection resources of the under attack system. This paper models the under attack server by using the queuing theory in which attack requests are recognized based on their long service time. Then it proposes a framework in which the defense issue is formulated as an optimization problem and employs the particle swarm optimization (PSO) algorithm to optimally solve this problem. PSO tries to direct the server to an optimum defense point by dynamically setting two TCP parameters, namely, maximum number of connections and maximum duration of a half-open connection. The simulation results show that the proposed defense strategy improves the performance of the under attack system in terms of rejection probability of connection requests and efficient consumption of buffer space.     

PTIR:一个用于检测恶意主机攻击的记录协议

移动代理作为一种分布计算和移动计算的支撑技术，得到广泛研究。但由于移动代理的迁移执行，引起一全新安全问题：如何保护遭主机攻击的移动代理？即恶意主机问题，从检测恶意主机攻击的角度出发，人们提出了基于参考状态（reference states)的方法，但目前所提出方法的开销都比较大。认为只需记录移动代理在各主机运行时的输入和运行后的结果即可，基于此，提出新的检测恶意主机攻击的协议PTIR(a protocol tracing inputs and results to detect malicious host‘s attacks)，比较分析表明，新协议的检测开销有较大降低。     

一种改进的TCP连接迁移安全机制

TCP连接迁移技术使网络可以在主服务器发生故障的情况下稳定地提供服务。该文分析基于椭圆曲线Diffie-Hellman密钥协商的连接迁移安全机制中存在的中间人攻击问题,利用改进的Helsinki协议进行连接密钥的协商,提出一种新的安全机制。该机制有效地保证了迁移选项的安全,利用安全哈希算法的抗碰撞性和安全性使攻击者难以猜测出连接标志和请求。     

安全高效的异构无线网络可控匿名漫游认证协议

分析传统的匿名漫游认证协议,指出其匿名不可控和通信时延较大的不足.针对上述不足,提出异构无线网络可控匿名漫游认证协议,远程网络认证服务器通过1轮消息交互即可完成对移动终端的身份合法性验证,当移动终端发生恶意操作时,家乡网络认证服务器可协助远程网络认证服务器撤销移动终端的身份匿名性.该协议在实现匿名认证的同时,还具有恶意匿名的可控性,有效防止了恶意行为的发生,且其通信时延较小.安全性证明表明,该协议在CK安全模型中是可证安全的.相对于传统漫游机制而言,该协议更适合于异构无线网络.     

DOMtegrity: ensuring web page integrity against malicious browser extensions

In this paper, we address an unsolved problem in the real world: how to ensure the integrity of the web content in a browser in the presence of malicious browser extensions? The problem of exposing confidential user credentials to malicious extensions has been widely understood, which has prompted major banks to deploy two-factor authentication. However, the importance of the “integrity” of the web content has received little attention. We implement two attacks on real-world online banking websites and show that ignoring the “integrity” of the web content can fundamentally defeat two-factor solutions. To address this problem, we propose a cryptographic protocol called DOMtegrity to ensure the end-to-end integrity of the DOM structure of a web page from delivering at a web server to the rendering of the page in the user’s browser. DOMtegrity is the first solution that protects DOM integrity without modifying the browser architecture or requiring extra hardware. It works by exploiting subtle yet important differences between browser extensions and in-line JavaScript code. We show how DOMtegrity prevents the earlier attacks and a whole range of man-in-the-browser attacks. We conduct extensive experiments on more than 14,000 real-world extensions to evaluate the effectiveness of DOMtegrity.

     

一种基于Active Replication的TCP连接容错技术

本文提出一种基于Active Replication的TCP连接容错技术（ARTCP）,采用两层的Cluster结构,并通过前端的分发器和聚合网关机维持多个同步的TCP连接副本,达到了相互容错的效果。测试结果表明,该技术不仅保证网络服务连接级的高可用性,而且具有恢复时间短、开销小的优势。