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Security 7 min. read

Container Security: Hardening Images and Protecting the Runtime

Containers provide isolation — but only when configured correctly. Best practices for secure containers from build to runtime.

devRocks Engineering · 22. February 2026 · Aktualisiert: 31. March 2026
Container Security Docker Kubernetes
Container Security: Hardening Images and Protecting the Runtime

The Container Security Chain

Container security begins with the base image and ends with runtime monitoring. Every stage presents an attack surface — and every stage can be secured.

Build Phase: Hardening Images

  • Minimal Base Images: Distroless or Alpine instead of Ubuntu — fewer packages, smaller attack surface.
  • Non-Root User: Containers should never run as root. Define an unprivileged user in the Dockerfile.
  • Read-Only Filesystem: Set the root filesystem to read-only and explicitly mount writable directories.
  • No Latest Tag: Pin base image versions to specific digests for reproducible builds.

Registry Phase: Scanning Images

  • Admission Controller: Kubernetes admission webhooks can block unsigned or unscanned images.
  • Image Signing: Cosign or Notary ensure that only verified images are deployed.

Runtime Phase: Monitor and Restrict

  • Security Contexts: Kubernetes security contexts enforce non-root, read-only filesystems, and capability drops.
  • Pod Security Standards: The three levels — Privileged, Baseline, and Restricted — as namespace-wide policies.
  • Runtime Security: Falco or Sysdig detect suspicious behavior in running containers.

Conclusion

Container security is not a product, but a process. At devRocks, we implement security at every stage — from Dockerfile review to runtime monitoring.

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Frequently Asked Questions

You can enhance the security of your container images by using minimal base images like Distroless or Alpine, never using root users, making the root filesystem read-only, and pinning base image versions to specific digests to ensure reproducible builds.
Best practices include implementing admission controllers in Kubernetes that block unscanned or unsigned images, as well as using image signing tools like Cosign or Notary to ensure image verification.
For runtime monitoring of containers, you can use Kubernetes Security Contexts to enforce non-root users and read-only file systems, as well as implement Pod Security Standards to enforce security policies at the namespace level.
Running containers as root significantly increases the attack surface, as an attacker could gain full control over the container system in the event of a compromise. It is safer to define unprivileged users to minimize the risk.
To ensure that only trusted container images are running in your environment, you should use an image scanning tool that checks images for security vulnerabilities, as well as implement image signing mechanisms to ensure the integrity and authenticity of the images.

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