Safety-critical systems become increasingly open and interconnected, which makes them a target of various cyberattacks. Such cyberattacks might jeopardise system safety and availability. Many safety-critical systems, such as railways, have a very long life cycle and hence, a large number of legacy components. The implementation of modern security protection mechanisms is often restricted due to the rigidness of legacy architecture and high re-certification costs. Therefore, it is desirable to efficiently utilise the potential already present in the system and enhance cybersecurity protection without major modifications. Safety-critical systems usually contain a high degree of redundancy required to achieve fault tolerance. In this paper, we investigate how to utilise redundancy to enhance cybersecurity protection. We demonstrate that by introducing diversity in the redundant architectures and implementing security monitoring, we can potentially enhance cybersecutiry protection of safety-critical systems.