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Container and Kubernetes Security Basics

15 September 2026

Container and Kubernetes Security Basics

Containers and Kubernetes accelerate modern application deployment, but they bring a distinct security surface: insecure images, over-privileged containers, and misconfigured cluster components. This article summarises the fundamental principles of container and Kubernetes security.

Layer 1: image security

A container is born from an image; if the image is insecure, so is the container.

  • Use trusted, minimal base images. A small image means a small attack surface.
  • Scan images for vulnerabilities before deployment and regularly.
  • Do not embed secrets in images. Passwords/keys persist in image layers; use secret-management mechanisms.

Layer 2: runtime and least privilege

  • Do not run as root. Run the container as an unprivileged user; avoid privileged mode.
  • Restrict capabilities. Grant only the kernel capabilities needed.
  • Make the filesystem read-only where possible.
  • Set resource limits. CPU/memory limits stop one container from starving its neighbours.

Layer 3: Kubernetes cluster security

  • Protect the API server. An internet-exposed, weakly authenticated Kubernetes API server can lead to full cluster compromise. Restrict access.
  • Authorize with RBAC. Grant each identity only the permissions it needs; default broad roles are dangerous.
  • Apply network policies. Restrict pod-to-pod traffic by default; a flat network invites lateral movement.
  • Manage secrets securely. Protect Kubernetes Secrets appropriately; do not keep them in plaintext config.

The shared principle: secure defaults

Most container security reduces to secure defaults: minimal images, unprivileged runtime, narrow RBAC, restricted networking. The component you leave most open defines the weakest link.

Summary

Container and Kubernetes security proceeds in three layers: secure/scanned minimal images, an unprivileged runtime, and a tight cluster configuration (protected API server, narrow RBAC, network policies). The common principle is secure defaults; the broadest-left component is the attacker’s first target.

Sources: Kubernetes Security Documentation, OWASP Docker Security Cheat Sheet, NIST SP 800-190.

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