The paper introduces a class of zero-sum games between the adversary and controller as a scenario for a 'denial of service' in a networked control system. The communication link is modelled as a set of transmission regimes controlled by a strategic jammer whose intention is to wage an attack on the plant by choosing a most damaging regime-switching strategy. We demonstrate that even in the one-step case, the introduced games admit a saddle-point equilibrium, at which the jammer's optimal policy is to randomize in a region of the plant's state space, thus requiring the controller to undertake a nontrivial response which is different from what one would expect in a standard stochastic control problem over a packet dropping link. The paper derives conditions for the introduced games to have such a saddle-point equilibrium. Furthermore, we show that in more general multi-stage games, these conditions provide 'greedy' jamming strategies for the adversary. (C) 2017 Elsevier Ltd. All rights reserved.