Over the past few years, interest in ICS/SCADA systems security has grown immensely. However, most of this interest has been focused on IP-connected SCADA networks, largely ignoring numerous deployments relying on other technologies such as wireless serial links. In this talk, I'll introduce a new GNU Radio module which lets you sniff SCADA networks that use a popular RF modem for their communications. I'll also describe the process of reverse-engineering the proprietary RF protocol used. Finally, I'll talk about the higher-layer protocols used in SCADA networks, including ModBus and DNP3, demonstrate how we are able to monitor the (unencrypted and unauthenticated) sensing and control systems used by a large electricity distribution network, and discuss some of its implications.