The Formal Methods knowledge area surveys the most relevant topics in formal methods for security. As a discipline, formal methods address foundations, methods and tools, based on mathematics and logic, for rigourously developing and reasoning about computer systems, whether they be software, hardware, or a combination of the two. The application of formal methods to security has emerged over recent decades as a well-established research area focused on the specification and proof of security properties of systems, their components, and protocols. We speak with CyBOK Formal Methods author David Basin for an overview of the topic.