start on dealing with this question systematically.

Albert, Jeong and Barabási showed that although a scalefree network provides better connectivity, this comes at a cost in robustness – an opponent can disconnect a network quickly by concentrating its firepower on well-connected nodes. In this paper, we have asked the logical next questions. What sort of defence should be planned by operators of such a network? And what sort of framework can be developed in which to test successive refinements of attack, defense, counterattack and so on?

First, we have shown that naive defences don’t work. Simply replacing dead hubs with new recruits does not slow down the attacker much, regardless of whether link replacement follows a random or scale-free pattern.

Moving from a single-shot game to a repeated game provides a useful framework. It enables concepts of evolutionary game theory to be applied to network problems.

Next, we used the framework to explore two more sophisticated defensive strategies. In one, potentially vulnerable high-order nodes are replaced with rings of nodes, inspired by a standard technique in anonymous communications. In the other, they are replaced by cliques, inspired by the cell structure often used in revolutionary warfare. To our surprise we 