In order to destroy a common type of network that scientists call “scale free”, it may be necessary to disrupt (or arrest) essentially every member, if we know nothing about the relative importance of each of the members. Having reliable information about the top 1% of the most important nodes in a network means that the system could be destroyed by attacking as few as one fourth of the network members. Knowing the relative importance of all the members will allow you to destroy a network by taking out about 7% of the nodes.

It should come as no surprise that crime rings and terrorist networks go to great trouble to keep their most powerful and highly connected members secret. The bottom line: secrecy is the best defense for networks under attack, and good intelligence is vital for taking networks down. The researchers note that their analysis is also applicable to controlling the spread of contagious disease through vaccinations in populations connected by social networks.

Original Paper: Lazaros Gallos et al.
Phys. Rev. Lett. 94, 188701 (2005), 13 May 2005