  In this paper we investigate the problem of optimal cache placement in the
presence of malicious mobile users in heterogeneous networks, where small-cell
base stations are equipped with caches in order to reduce the overall backhaul
load. In particular the malicious users aim at maximizing the congestion of
files at the backhaul, i.e., at maximizing the average backhaul rate. For that
adversarial model, we derive the achievable average backhaul rate of the
heterogeneous network. Moreover, we study the system performance from a
game-theoretic perspective, by naturally considering a zero-sum Stackelberg
game between the macro-cell base station and the malicious users. We then
thoroughly investigate the system performance in the presence of adversaries
and we analyze the influence of the system parameters, such as the network
topology and the capabilities of the small-cell base stations, on the overall
performance of edge caching at the Stackelberg equilibrium. Our results
highlight the impact of the malicious users on the overall caching performance
of the network and they furthermore show the importance of an adversary-aware
content placement at the small-cell base stations.
