Modern industrial equipment are networked to interact with both internal and external systems, enabling automated decision-making with minimal or no human intervention. While this new environment creates efficiencies, it exposes the environment to cyber threats. This chapter explores the use of cybersecurity testbeds to study best practices in architecting and defending environments that contain industrial systems. Cybersecurity testbeds – physical, virtual, and hybrid – are used in different sectors for research and validation. Virtual testbeds hold promise as they enable design flexibility, reconfiguration, and scale to support various types of research studies. This chapter discusses the value of virtual cybersecurity testbeds and demonstrates a case study on the use of virtual testbeds using a simple industrial control system and a common attack. The concepts apply to more complex set ups and more complex attack structures. Virtual cybersecurity testbed can support researchers, practitioners, and educators interested in defending critical infrastructure environments and industrial systems.