What are the best practices for securing multi-tenant Kubernetes clusters while using minimal images?

Minimal images definitely help, but they're just one part of the security puzzle. In my experience, using namespace isolation, strict RBAC (Role-Based Access Control), and default deny network policies are equally important. Without these controls, relying solely on minimal images won’t effectively prevent lateral movement between tenants. Secure your cluster on multiple levels for robust protection.

Using minimal images like distroless is a solid starting point since they eliminate shells and utilities that attackers might exploit for lateral movement. However, to achieve true isolation in a multi-tenant setup, you should prioritize Network Policies. Implementing a default deny-all policy is crucial to prevent Tenant A from communicating with Tenant B, even in the event of a security breach. Additionally, consider using sandboxed runtimes like gVisor or Kata Containers for an extra layer of security against potential kernel exploits. Also, make sure to enforce strict Pod Security Standards by dropping all unnecessary Linux capabilities and running containers as non-root with read-only filesystems.