Supervisory Control and Data Acquisition (SCADA) systems monitor and control industrial systems of national importance, including but not limited to the electric power grid, oil and gas refineries, water supply and sewage systems, and gas pipelines. They are an integral part of a nation's critical infrastructure. As such, the reliability and availability of these systems are extremely important. Once SCADA systems are running reliably, changes to the hardware or software are typically avoided. As a result, many of these systems rely upon hardware and software systems that are years or even decades in age. Over time and for the purpose of cost optimization, SCADA systems have become increasingly reliant upon commercial-off-the-shelf (COTS) products. Many of these products have known vulnerabilities that are expected to be patched or replaced quite often to mitigate potential attacks. However, frequent patches and updates are often unfeasible in a SCADA system. The requirements of reliability and availability may outweigh the potential benefits. An additional security issue is that in order to enable remote system management, SCADA systems are becoming increasingly connected directly to corporate networks as well as the Internet thus making it easier for an adversary to connect to a system in order to exploit known vulnerabilities. Moving Target Defense (MTD) is a security approach used in many common computer systems to help make them less easily compromised. A MTD seeks to provide additional protection to all protected programs even if those programs have known vulnerabilities. It does not seek to fix any particular software vulnerability but, instead, seeks to make any such vulnerability more difficult to exploit. Other security solutions elaborated for our common computer systems and networks, such as frequent software patching, might not be applicable for SCADA systems due to their specific requirements and constraints. However, there has not been much academic discussion of applying Moving Target Defenses to SCADA systems. We analysed several different MTD techniques for their suitability as defense of various components of SCADA systems. Our determination is that there are several MTD approaches that are feasible for use in SCADA systems.