The next-generation electrical power system is focusing on reliable, automated, and secure power grid by using information and communication technology (ICT). To realize the new generation of power grid, the communication network is a decisive piece of the entire smart grid. Communication infrastructure in smart grids is a combination of both wired and wireless technologies. The salient features of wireless technology makes it attractive but the easy access to the radio medium in wireless communication increases the risk of security attacks. Consequently, the concern for cyber security has become an important issue to be addressed in a smart grid network. Intrusion detection and response to these intrusions in a timely manner is a way to improve system integrity. In this paper, we focus on a medium access control (MAC) layer intrusion detection system for wireless networks in smart grids. We propose a multi-level intrusion detection response system (IDRS) framework based on the perception of defense-in-depth. Through a simple simulation study, we verify the working of our proposed framework.