The Cloud Native Security “4C’s” model is commonly presented as Code, Container, Cluster, Cloud, ordered from the layer you control most directly to the one you control least—therefore D is correct. The idea is defense-in-depth across layers, recognizing that responsibilities are shared between developers, platform teams, and cloud providers.
Code is where users have the most direct control: application logic, dependencies, secure coding practices, secrets handling patterns, and testing. This includes validating inputs, avoiding vulnerabilities, and scanning dependencies. Next is the Container layer: building secure images, minimizing image size/attack surface, using non-root users, setting file permissions, and scanning images for known CVEs. Container security is about ensuring the artifact you run is trustworthy and hardened.
Then comes the Cluster layer: Kubernetes configuration and runtime controls, including RBAC, admission policies (OPA/Gatekeeper), Pod Security standards, network policies, runtime security, audit logging, and node hardening practices. Cluster controls determine what can run and how workloads interact. Finally, the Cloud layer includes the infrastructure and provider controls—IAM, VPC/networking, KMS, managed control plane protections, and physical security—which users influence through configuration but do not fully own.
The model’s value is prioritization: start with what you control most (code), then harden the container artifact, then enforce cluster policy and runtime protections, and finally ensure cloud controls are configured properly. This layered approach aligns well with Kubernetes security guidance and modern shared-responsibility models.
