using different sizes of rings and cliques. Ring size appears to make little difference; rings are just not an effective defence other than in the very short term. However, varying the clique size yields the results displayed in Figure \[fig:BA03\].

\[htbp\] ![Clique recovery with different clique sizes under a centrality attack []{data-label="fig:BA03"}](vertex-order-attack-cliques-sizes.eps "fig:")\
![Clique recovery with different clique sizes under a centrality attack []{data-label="fig:BA03"}](centrality-attack-cliques-sizes.eps "fig:")

This shows that under a centrality attack, the performance of the defense increases steadily with the size of the clique. There is still a phase transition after about 14 rounds or so after which the largest connected component becomes significantly smaller, but the size of this equilibrium component increases steadily from about 150 with clique size 8 to almost 300 at clique size 20.

Defence Evolution – Second Round
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Now that we know centrality attacks are powerful, we have tried a number of other possible defences. The most promising at present appears to be a compound defence based on cliques and delegation.

The idea behind delegation is fairly simple. A node that is becoming too well-connected selects one of its neighbours as a ‘deputy’ and connects it to a second neighbour, with which it 