ITU-T G.9959 wireless connectivity is increasingly incorporated in the critical infrastructure. However, evaluating the robustness and security of commercially-available products based on this standard is challenging due to the closed-source nature of the transceiver and application designs. Given that ITU-T G.9959 transceivers are being used in smart grids, building security systems and safety sensors, the development of reliable, open-source tools would enhance the ability to monitor and secure ITU-T G.9959 networks. This chapter discusses the ITU-T G.9959 wireless standard and research on ITU-T G.9959 network security. An open-source, software-defined radio implementation of an ITU-T G.9959 protocol sniffer is used to explore several passive reconnaissance techniques and deduce the properties of active network devices. The experimental results show that some properties are observable regardless of whether or not encryption is used. In particular, the acknowledgment response times vary due to differences in vendor firmware implementations.