Intruder tracking and herding problems are crucial in several applications. In this paper a game theoretic coordination protocol for multi-mobile robot systems is proposed to tackle both problems simultaneously. Defender robots move according to computed Nash equilibria to herd the intruder into a safe area while preventing its access to one or more protected areas. The concept of a virtual barrier is presented to induce defenders to automatically and uniformly deploy along the barrier in order to drive intruder away from the protected areas and toward the safe one. Simulation results are reported to validate the proposed approach.