WIND: Workload-aware INtrusion detection

Abstract

Intrusion detection and prevention systems have become essential to the protection of critical networks across the Internet. Widely deployed IDS and IPS systems are based around a database of known malicious signatures. This database is growing quickly while at the same time the signatures are getting more complex. These trends place additional performance requirements on the rule-matching engine inside IDSs and IPSs, which check each signature against an incoming packet. Existing approaches to signature evaluation apply statically-defined optimizations that do not take into account the network in which the IDS or IPS is deployed or the characteristics of the signature database. We argue that for higher performance, IDS and IPS systems should adapt according to the workload, which includes the set of input signatures and the network traffic characteristics. To demonstrate this idea, we have developed an adaptive algorithm that systematically profiles attack signatures and network traffic to generate a high performance and memory-efficient packet inspection strategy. We have implemented our idea by building two distinct components over Snort: a profiler that analyzes the input rules and the observed network traffic to produce a packet inspection strategy, and an evaluation engine that pre-processes rules according to the strategy and evaluates incoming packets to determine the set of applicable signatures. We have conducted an extensive evaluation of our workload-aware Snort implementation on a collection of publicly available datasets and on live traffic from a border router at a large university network. Our evaluation shows that the workload-aware implementation outperforms Snort in the number of packets processed per second by a factor of up to 1.6x for all Snort rules and 2.7x for web-based rules with reduction in memory requirements. Similar comparison with Bro shows that the workload-aware implementation outperforms Bro by more than six times in most cases. © Springer-Verlag Berlin Heidelberg 2006.