  We formulate a resource-planning game between an attacker and a defender of a
network control system. We consider the network to be operating in closed-loop
with a linear quadratic regulator (LQR). We construct a general-sum,
two-player, mixed strategy game, where the attacker attempts to destroy
communication equipment of some nodes, and thereby render the LQR feedback gain
matrix to be sparse, leading to degradation of closed-loop performance. The
defender, on the other hand, aims to prevent this loss. Both players trade
their control performance objectives for the cost of their actions. A Mixed
Strategy Nash Equilibrium (MSNE) of the game represents the allocation of the
players' respective resources for attacking or protecting the network nodes. We
analyze the dependence of a MSNE on the relative budgets of the players as well
as on the important network nodes that must be preserved to achieve a desirable
LQR performance. MSNE is computed using nonlinear programming. Results are
validated using the New England power system model, and it is shown that
reliable defense is feasible unless the cost of attack is very low or much
smaller than the cost of protection per generator.
