An identifier network (IN), as one of the promising network architectures to solve the IP dual properties problems, has been applied in many areas, including Internet of Things (IoT) for smart cities scenario. The separation mechanisms of an access/core network and identifier/location can benefit IoT in terms of trust management, access control, and privacy protection. The core network in IN is independent of the access network by introducing two namespaces, which makes the core network difficult to be attacked but easy for trust management. However, access network, such as access wireless sensor network (WSN), is facing serious trust and security challenge. Therefore, this article addresses this problem by using network address shuffling. We present an optimization framework of defense cost for IoT security and formulate it as a stochastic cost optimization problem by considering the impacts of network address shuffling control, network autoimmunity control, and defense cost. To improve its generality, we adopt a Lyapunov optimization theory and transform the formulated optimization problem into a queue stability problem, and further decompose the queue stability problem into two subproblems to solve the initial optimization problem. Finally, a novel stochastic cost minimization mechanism (SCMM) consisting of two algorithms for the derived subproblems is proposed. Through logical theoretical analyses, it is proved that our proposed mechanism can achieve the optimized results while maintaining the security of each access WSN and guaranteeing the limited network resources. The extensive simulation results verify that the tradeoff between defense strategy and limited network resources can be well tackled by the balancing factor.