A Network Security Classification Game

We consider a network security classification game in which a strategic defender decides whether an attacker is a strategic spy or a naive spammer based on an observed sequence of attacks on fileor mail-servers. The spammer’s goal is attacking the mail-server, while the spy’s goal is attacking the file-server as much as possible before detection. The defender observes for a length of time that trades-off the potential damage inflicted during the observation period with the ability to reliably classify the attacker. Through empirical analyses, we find that when the defender commits to a fixed observation window, often the spy’s best response is either full-exploitation mode or full-confusion mode. This discontinuity prevents the existence of a pure Nash equilibrium in many cases. However, when the defender can condition the observation time based on the observed sequence, a Nash equilibrium often exists.