Container Security

Author: Damien Burks

Now that you’ve explored the foundations of Application Security, the Secure SDLC, and the principles of DevSecOps, it’s time to focus on one of the most important parts of modern software delivery: Container Security.

Overview

Containers have changed how we build, package, and deploy software. They make applications portable, consistent, and fast to ship, but they also introduce new attack surfaces that must be managed carefully. From outdated base images to leaked secrets and over-privileged containers, insecure configurations can make containers the easiest entry point into your environment.

In DevSecOps, container security isn’t just about scanning images. It’s about embedding security throughout the entire container lifecycle... from build, to ship, to runtime.

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You can find the original image here: Securing Containers from Build to Runtime | Microsoft Defender for Cloud Also, containers give speed, but speed without security invites risk. Treat every image and runtime as part of your security perimeter.

Common Attack Surfaces

To secure containers effectively, you need to understand where they’re most vulnerable:

Surface	Description
Base Images	Outdated or unverified base images may include known CVEs and hidden dependencies.
Image Layers	Each layer can add unnecessary files, secrets, or unpatched binaries if not reviewed.
Secrets Exposure	Hardcoded credentials or unencrypted environment variables often end up baked into images.
Container Runtime	Containers running as root or with privileged access can compromise the host system.
Networking	Misconfigured networks may expose internal services to the public internet.
Registry Security	Using unverified public images or insecure registries risks introducing malicious software.

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Most container breaches stem from configuration mistakes, not advanced exploits. Start by securing the basics.

The Container Security Lifecycle

Container security follows the same shift-left philosophy as DevSecOps: secure early, monitor continuously, and automate everything.

1. Build Phase

• Scan base images and dependencies for known vulnerabilities.
• Use minimal base images to reduce the attack surface.
• Enforce consistent image signing and tagging.
• Maintain a Software Bill of Materials (SBOM) to track what’s inside every image.

2. Ship Phase

• Store only trusted images in private or verified registries.
• Apply access controls and automated scanning at the registry level.
• Sign and verify images before deployment.
• Avoid using the “latest” tag. Always version explicitly for traceability.

3. Run Phase

• Run containers with least privilege and never as root.
• Apply resource limits (CPU, memory) to prevent denial-of-service conditions.
• Enable runtime monitoring and anomaly detection.
• Isolate workloads using namespaces, cgroups, and sandboxing.

Best Practices for Container Security

1. Adopt Immutable Infrastructure
   Treat containers as disposable. Rebuild images to patch, never modify live ones.

2. Minimize the Attack Surface
   Use lightweight base images (for example Alpine or Distroless) and remove unnecessary packages.

3. Scan Early and Often
   Integrate container scanning into CI/CD pipelines to catch vulnerabilities before deployment.

4. Protect Secrets
   Inject secrets securely at runtime using tools like Vault or Secrets Manager. Never bake them into images.

5. Implement Image Signing and Verification
   Use tools like Cosign or Notary to verify image integrity before deployment.

6. Monitor Runtime Behavior
   Watch for abnormal processes, network activity, and privilege escalations. Tools like Falco can help.

7. Secure Registries
   Restrict access to trusted users and enforce scanning on every pushed image.

Recommended Tools

Tool	Purpose
Trivy	Scans images, file systems, and repos for vulnerabilities and secrets.
Grype / Anchore Engine	Performs deep image analysis and compliance reporting.
Clair	Scans Docker and OCI images for known vulnerabilities.
Docker Scout	Integrates vulnerability insights directly into Docker builds.
Falco	Detects runtime anomalies and suspicious behavior.
Cosign	Signs and verifies images for integrity and provenance.

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Combine multiple tools to cover different stages of the container lifecycle. No single scanner does it all.

Practice What You’ve Learned

Now it’s your turn to apply what you’ve learned.

1. Choose a small containerized app (for example, a Flask API or Node.js microservice).
2. Scan your image for vulnerabilities using Trivy or Grype.
3. Add runtime monitoring with Falco or a similar tool.
4. Review your Dockerfile for security misconfigurations.

✅ Capstone Goal: Show that you can identify and remediate vulnerabilities across the container build, ship, and run phases.

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Remember, security doesn’t end at deployment. Containers must be monitored, patched, and rebuilt regularly to stay secure.

Recommended Resources

Recommended Certifications

Certification	Provider	Why It’s Relevant
Docker Certified Associate (DCA)	Docker	Validates container lifecycle and security fundamentals.
Certified Kubernetes Application Developer (CKAD)	CNCF	Reinforces container orchestration and deployment security.
CompTIA Security+	CompTIA	Strengthens foundational security knowledge.
Certified DevSecOps Professional (CDP)	Practical DevSecOps	Focuses on container scanning and policy automation.

📚 Books

Book Title	Author	Link	Why It’s Useful
Container Security: Fundamental Technology Concepts That Protect Cloud Native Applications	Liz Rice	Amazon	Explains how containers work under the hood and how to secure them effectively throughout their lifecycle.
Application Container Security Guide - NIST SP 800-190	National Institute of Standards and Technology	Amazon	Provides official NIST guidance on container threats, mitigations, and best practices for secure deployments.
Kubernetes Security	Liz Rice	Amazon	Provides a clear, technical guide to securing Kubernetes workloads and understanding container threats.

🎥 Videos

What is Container Security?

How To Secure & Harden Docker Containers