To tighten Kubernetes cluster security, it's essential to implement industry-standard best practices. This includes not keeping secrets in environment variables, using strong authentication and authorization, disabling the NET_RAW capability, and avoiding sharing host namespaces and IPC. Additionally, using Role-Based Access Control (RBAC), isolating nodes from public networks, avoiding running containers in privileged mode, checking for unsafe `/proc` mount, and having a rolling update strategy can also help improve security. Furthermore, achieving Kubernetes security is challenging due to the constantly changing ecosystem, but automation tools like CAST AI's Cloud Security feature can prioritize security issues automatically.