The first step to grappling with the security problems that face modern supervisory control and data acquisition (SCADA) systems and industrial control networks is investing in research and education. However, because of the specialized nature of industrial control systems and networks, the cost of even a modest testbed for research or education can quickly get out of hand. Hardware-based testbeds are often not practical due to budgetary constraints, and they do not readily scale to meet educational demands. Software simulations are a cost-effective alternative, but current solutions focus primarily on network aspects, not the implementation of field device and application functionality. This paper describes the design and implementation of a programmable logic controller emulator using VMware. The emulator solution is both cost-effective and scalable. Moreover, it can accurately replicate real-world field device functionality to meet research and educational requirements.