An Industrial Control System (ICS) can be seen as a comprehensive class of automation systems employed to provide control and monitoring functionalities in manufacturing and industrial sectors. There has been a trend to include critical infrastructure across ICS sectors for safe and efficient operations. However, integrating critical infrastructure with public networks has exposed ICSs to cyber-attacks. As traditional ICSs have not been designed to handle security threats, existing vulnerabilities should be identified, and proper methods must be developed to make systems cyber-resilient. In this paper, we discuss the challenges of cyber security resilience in ICS networks. We provide the functionalities of an ICS architecture and vulnerabilities in an ICS network. Significantly, we discuss defence-in-depth for ICS networks based on prevention, detection, and incident response, and the incorporation of zero trust principles. Finally, we outline potential future activities to address those challenges.