Risk homeostasis and network security [Editor's Note]

This Special Issue is dedicated to the topic of network intrusion detection. The wide use of many varieties of intrusion detection systems reveals a certain degree of acceptance that, despite our best intentions for building secure systems, there is always enough opportunity for attacks, possibly exploiting weaknesses of the very systems we thought to be secure. Moreover, even though attacks usually follow patterns that can be subsequently used to detect them, they also happen to be the product of intelligent adversaries - humans. The ability to orchestrate ever more elaborate attacks, exhibiting patterns not seen before, means that we expect an IDS to be ready to discern new patterns found to be conceivably detrimental to the security requirements of a system. Intrusion detection systems are sometimes criticized as doing too little too late. However, there are cases where even a late response is better than no response at all.