  Ensuring a car's internal systems are free from security vulnerabilities is
of utmost importance, especially due to the relationship between security and
other properties, such as safety and reliability. We provide the starting point
for a model-based framework designed to support the security testing of modern
cars. We use Communicating Sequential Processes (CSP) to create architectural
models of the vehicle bus systems, as well as an initial set of attacks against
these systems. While this contribution represents initial steps, we are mindful
of the ultimate objective of generating test code to exercise the security of
vehicle bus systems. We present the way forward from the models created and
consider their potential integration with commercial engineering tools
