In this paper, we consider the problem of interferers for cooperative spectrum sensing in a centralized cognitive radio network comprising N cognitive radios (CRs) and one fusion center (FC) in the presence of a fixed interferer. The design metric chosen is the error probability. We prove the existence of a saddle-point in the minimax game between the interferer and the CR network. An optimal solution is found that maximizes the objective with respect to the interferer's parameters and minimizes the same with respect to the CR network's parameters. We show that the probability of error is a quasi-convex function with respect to the network's parameters and a monotone function with respect to the interferer's parameters. We also present numerical results that corroborate our theoretical results.