📝 Secure Your Dockerfiles: Best Practices and Vulnerability Scanning Tools

1. Introduction

Security is often overlooked during container builds. A single insecure Dockerfile can expose your entire infrastructure to attackers. This guide explains how to write secure Dockerfiles and use vulnerability scanning tools to ensure your images are safe before deployment.

2. Common Dockerfile Security Risks

• Using outdated or bloated base images

• Running containers as root

• Hardcoding secrets or API keys

• Installing unnecessary packages

• Not scanning or validating images before release

Each of these risks increases your attack surface and weakens your DevOps security posture.

3. Secure Dockerfile Practices

✔ Use Minimal Base Images

Prefer lightweight images like alpine, distroless, or slim variants.

✔ Pin All Versions

Ensure reproducibility and predictable builds. Example:
node:18.17.1-alpine

✔ Prefer COPY Over ADD

Use ADD only when you need extraction or remote fetching.

✔ Use .dockerignore

Exclude unnecessary or sensitive files from your image.

✔ Run as Non-Root

Improve container isolation and reduce impact of exploit attempts.

4. Vulnerability Scanning Tools

These tools help identify known CVEs, misconfigurations, and outdated dependencies.

5. Using Trivy to Scan an Image

Install Trivy

Scan an Image

Scan a Dockerfile or Config

6. Automating Scans in CI/CD

Example GitHub Action for automatic scanning:

This ensures every build is scanned before deployment.

7. Conclusion

Security must be embedded into your DevOps pipeline—not added as an afterthought. By applying Dockerfile security best practices and running regular vulnerability scans, you significantly reduce risk and strengthen your containerized infrastructure.

Tomorrow’s post will cover CI/CD Pipeline Design with Jenkins—stay tuned!