Constructing optimal reconfigurable pattern matching tools for information security

Abstract

Signature-based security tools such as network intrusion detection systems, anti-virus scanners, filters against network worms and other similar systems perform in real time computation-intensive task of multi-pattern string matching against tens of thousands or even millions of predefined malicious patterns. Due to rising traffic rates, increasing number and sophistication of attacks and the collapse of Moore's law for sequential processing, traditional software solutions can no longer meet the high requirements of today’s security challenges. Therefore, designers pay more attention to hardware approaches to accelerate pattern matching. The reconfigurable devices based on Field Programmable Gate Arrays (FPGA) combining the flexibility of software and the near-ASIC performance, have become increasingly popular for this purpose. The state-of-the-art solutions made in this area around the world were analyzed. There are three main approaches to fulfill the pattern matching using FPGA. The techniques (and underlying technologies) of these approaches are: content addressable memory (based on digital comparators), Bloom filter (based on hash-functions) and Aho-Corasick algorithm (based on finite automata). But none of them shows clear advantages over others. In this article, we propose a set of methods to increase the effectiveness of reconfigurable security tools by synthesizing optimal recognition modules that maximize the benefits of each approach. The Parallel Combination Method divides a set of patterns between several matching blocks that use different approaches to better fit each of them. The Sequential Cascading Method processes patterns in parts: if the first fragment does not match, the rest can be ignored. The Vertical Join Method couples together different approaches or techniques in a single unit to provide higher efficiency of the resulting device. The optimization procedure maximizes efficiency gains for each method. The methods and methodologies presented in this study will allow developers to create more efficient reconfigurable tools for information security systems.