In this paper, we study using game theory the problem of detecting intrusions in wired infrastructure networks. Detection is accomplished by sampling a subset of the transmitted packets over selected network links or router interfaces. Given a total sampling budget, our framework aims at developing a network packet sampling strategy to effectively reduce the success chances of an intruder. We consider two different scenarios: (1) A well informed intruder divides his attack over multiple packets in order to increase his chances of successfully intruding a target domain. (2) Different cooperating intruders distribute the attack among themselves each send their attack fragments to the target node. Each of the packets containing a fragment of the attack is transmitted through a different path using multipath routing, where each path is selected with a different probability. Knowing that, if these packets are independently analyzed then the intrusion will not be detected, i.e., a series of...