Snort与防火墙联动防御3G网络信令攻击

【作者】 徐湛；

【导师】 李景涛； 倪重匡；

【作者基本信息】 复旦大学 ， 软件工程， 2009， 硕士

【摘要】 3G网络的发展和应用普及,丰富了移动通信服务的内容,给用户带来了诸多便利。越来越多的信息由3G网络承载,随之也带来网络安全方面许多新的问题。近期信令攻击引起了产业界和学术界的重视,这是一种利用3G网络信令平面漏洞的新型拒绝服务攻击。它的基本特征是：低速率、小流量的攻击流、易实现对多目标的攻击、并且危害很大,严重时可造成整个城市的3G网络瘫痪。针对信令攻击,目前还没有有效的检测和防御手段。这主要是因为传统的拒绝服务攻击都具有高速率,大流量的特征,因此入侵检测系统传统上主要根据这个特征设计并实现攻击检测。这使得低速率、小流量的信令攻击包可轻易地混入正常的数据包中,绕过传统的入侵检测系统。本文首先介绍3G网络的架构和特点,分析了目前威胁3G网络的主要安全隐患,着重分析了DoS攻击对3G网络危害的严重性；接着给出了信令攻击的模型,并在仿真环境下进行模拟攻击以观测其危害性；然后给出一种CUSUM算法的改进方案：基于时间差统计的信令攻击检测方法,给出检测方法的数学描述,基于开源入侵检测系统Snort,以插件形式在Snort中实现了检测方法；在仿真环境中进行实验验证,观测其防御效果,并提出优化其性能的改进方案。最后,设计并实现了检测系统与防火墙联动的解决方案,使得系统具有阻断信令攻击的能力。本文的主要工作包括：1.针对3G网络低速信令攻击,给出一种基于CUSUM算法的改进方案：时间差统计检测法。2.基于开源的入侵检测系统snort实现了上述检测方法,由于很多商用入侵检测系统是基于snort实现的,本文的实现可以直接应用于这些系统,改善其检测性能。3.在仿真环境下实验,进行性能评估。上述检测方法可以在信令攻击产生很大的危害之前,就被成功检测出来,表明提出的检测方法达到了预期效果。4.在实验中,通过对多次检测的结果进行分析比较,为时间差统计检测法的参数选择提供了一定的参考标准。5.实现集成了检测信令攻击插件的Snort系统与IpTables防火墙的联动,将Snort检测到的恶意IP地址提交给防火墙,让防火墙动态建立相应的过滤规则,使得整个系统具有防御信令攻击的能力。更多还原

【Abstract】 With the development of 3G wireless network, a variety of mobile services are provided, which brings various kinds of convenience to the users. More and more information are transmitted efficiently, via 3G wireless network. In the meantime, new problems are rising. Recently, Signaling attacking has become increasingly attractive in industrial and academic circles. This kind of attach exploit the leak of control plane in 3G network, which has the characteristic of low-volume and low-rate. Also, it has much mischief and can bring down the entire 3G network in a city.Currently, there is no efficient method to detect Signaling Attack. The low-volume, low-rate nature of the signaling attack allows it easily been injected into normal packages, and avoid detection by existing intrusion detection algorithms, which are often rate or volume-based. So, it is heightened and considered to be a famous technique problem.In this article, we will first introduce the architecture of 3G wireless network and analyze its security holes, mainly on the hazard of DOS attack. Then, we identify the signaling attack model, and demonstrate its impact in simulations. After that, we present an detection method: Statistical Time Difference Detection Method, show its mathematical description, and implement it as an add-in in open source Snort system. At last, we evaluate this detection method in trace-driven simulations, and present plans to optimize its performance.The main work in this article includes:1. We present a detection method:Statistical Time Difference Detection Method to defend low-rate Signaling attack in 3G wireless network.2. Implement the method as an add-in in open source Snort system. As many enterprise detection systems are based on Snort, it can be easily integrated into other systems to improve their detection performance.3. Through the trace-driven simulations, we demonstrate that the algorithm is robust and can identify an attack in its inception, before significant, damage is done.4. Via the trace-driven simulations, we compared all the result of different chosen parameters, and present how to choose the parameter in the detection method.5. We present plans to optimize its performance, which provides the references for detecting the variant of Signaling attack in future.6. Coordinate the firewall, IpTables, with Snort. Create corresponding block rules for the malicious IP addresses detected by Statistical Time Difference Detection Method, to enhance the system’s ability of defending signaling attack.更多还原