Evaluating intrusion prevention systems with evasions

Summary Intrusion prevention systems have become a common security measure in the past 20 years. Their promise is the possibility to prevent known attacks against vulnerable, unpatched devices inside enterprise networks. However, evasion techniques that enable the attacker to evade the eye of the intrusion prevention system are a potential problem for this capability. These techniques take advantage of the robustness principle that has guided designers to create systems that will try to recreate protocol content from any input they receive. In this work, we evaluated the effectiveness of 35 well‐known evasions against 9 commercial and 1 free, state‐of‐the‐art, intrusion prevention systems. We conducted 4 experiments with one million attacks against each device. Each system lets a significant amount (0.1%‐45%) of attacks pass through unrecognized. Our results show that most existing intrusion prevention systems are vulnerable against evasions. Evasion techniques enable an attack to pass an intrusion prevention system unnoticed. We evaluated 10 IPS, running 4 million well‐known attacks with evasions against each device. Each system lets a significant amount of attacks pass through.