This tool has been provided by
Ente per le Nuove Tecnologie, l'Energia e l'Ambiente (ENEA):

NAT Network Analysis Tool is a web tool for the analysis of topological parameters of a graph. The tool applies the ideas and methods of Complexity Science to the analysis and protection of large complex critical infrastructures.

This tool is freely available from the site:
http://irriis.nat.ylichron.it/default.aspx subjected to a free registration

A user's manual is available here and at the NAT site, accessible after the Registration.