  We consider a two-player zero-sum network routing game in which a router
wants to maximize the amount of legitimate traffic that flows from a given
source node to a destination node and an attacker wants to block as much
legitimate traffic as possible by flooding the network with malicious traffic.
We address scenarios with asymmetric information, in which the router must
reveal its policy before the attacker decides how to distribute the malicious
traffic among the network links, which is naturally modeled by the notion of
Stackelberg equilibria. The paper focuses on parallel networks, and includes
three main contributions: we show that computing the optimal attack policy
against a given routing policy is an NP-hard problem; we establish conditions
under which the Stackelberg equilibria lead to no regret; and we provide a
metric that can be used to quantify how uncertainty about the attacker's
capabilities limits the router's performance.
