  We introduce the concept of control centrality to quantify the ability of a
single node to control a directed weighted network. We calculate the
distribution of control centrality for several real networks and find that it
is mainly determined by the network's degree distribution. We rigorously prove
that in a directed network without loops the control centrality of a node is
uniquely determined by its layer index or topological position in the
underlying hierarchical structure of the network. Inspired by the deep relation
between control centrality and hierarchical structure in a general directed
network, we design an efficient attack strategy against the controllability of
malicious networks.

Physics and Society;Statistical Mechanics;Social and Information Networks