**6. Conclusions**

In this chapter we provide a methodology for the definition of a defensive strategy via prioritizing the critical nodes of the network. Due to the complexity of a CI, the adoption of a unique metric for the identification of the node criticality is simplistic, to this end we propose a strategy, based on the AHP, able to merge multiple metrics which take into different aspects of the network. Moreover, the proposed aggregation procedure is applicable also in case of incomplete data. Among the multiple metrics applicable in the merging process, in this chapter we propose two metrics characterized by a focus on the network connectivity. In the one hand the critical index is computed on the basis of a multi objective optimization problem. Assuming an attacker perspective and knowing the topology of the network, the problems aims at identifying the nodes whose removal compromise the connectivity of the entire system. On the other hand, we propose the adoption of the Shapley value as a criticality evaluation by defining a cooperative game among the nodes of the network. Finally, we propose the definition of a defensive strategy that assigns to each node a removal cost proportional to the holistic indicator. Future improvement will be devoted to the inclusion of a final check able to include a final validation based on expert opinions. One of the possible validity check is based on the well-known face validity approach [19], it refers to the transparency or relevance of a test as it appears to test participants.

*A Strategy to Improve Infrastructure Survivability via Prioritizing Critical Nodes… DOI: http://dx.doi.org/10.5772/intechopen.95367*
