Secure Coding & OWASP Top 10 for Backend · Lesson

Container Security (Docker/Kubernetes)

Implement secure practices for building, deploying, and managing containerized applications using Docker and Kubernetes, including image scanning and network policies.

Container Security (Docker/Kubernetes) is a free Secure Coding & OWASP Top 10 for Backend lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Secure Coding & OWASP Top 10 for Backend learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Introduction to Container Security

Welcome to Container Security! Here, we'll explore how to protect your applications when they run inside containers like Docker and are orchestrated by systems like Kubernetes.

Containers offer great flexibility and efficiency, but they also introduce new security challenges that need careful attention.

Minimize Container Images

Smaller container images mean less attack surface. Remove unnecessary tools, libraries, and files from your final image.

Using multi-stage builds and minimal base images (like Alpine Linux variants) are excellent strategies.

FROM openjdk:17-jdk-slim AS builder
WORKDIR /app
COPY . .
RUN javac Main.java

FROM openjdk:17-jre-slim
WORKDIR /app
COPY --from=builder /app/Main.class .
CMD ["java", "Main"]

Use Trusted Base Images

Always start with official and well-maintained base images from trusted registries. Unofficial images might contain vulnerabilities or even malicious code.

Verify sources: Only pull images from reputable vendors or official repositories.
Scan regularly: Even official images can have vulnerabilities; scan them often.

Principle of Least Privilege

Run your containers with the minimum necessary permissions. This limits the damage if a container is compromised.

Run as non-root: Avoid running processes as the root user inside the container.
Drop capabilities: Remove Linux capabilities (e.g., NET_ADMIN, SYS_ADMIN) that your application doesn't need.

docker run --user 1000:1000 \
  --cap-drop=ALL \
  my-secure-app

Scan Container Images for Vulnerabilities

Integrate automated image scanning tools (like Trivy, Clair, or vulnerability scanners from cloud providers) into your CI/CD pipeline.

Scan images early and often to detect known vulnerabilities in your dependencies and operating system layers before deployment.

Kubernetes Network Policies

Network Policies in Kubernetes allow you to control which pods can communicate with each other and with external network endpoints.

By default, pods can communicate freely. Network policies enforce segmentation, creating a firewall around your pods.

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: deny-all-ingress
  namespace: default
spec:
  podSelector: {}
  policyTypes:
    - Ingress

Secure Secrets Management

Sensitive information like API keys, database passwords, and private certificates should never be hardcoded into images or configuration files.

Use Kubernetes Secrets, HashiCorp Vault, or cloud-specific secret managers to store and inject secrets securely at runtime.

apiVersion: v1
kind: Secret
metadata:
  name: my-app-secret
type: Opaque
data:
  api_key: YmFzZTY0ZW5jb2RlZHNlY3JldA== # base64 encoded value
  db_password: cGFzc3dvcmQ=

Runtime Security & Monitoring

Even with robust build-time security, runtime protection is crucial. Monitor container behavior for suspicious activities.

Tools like Falco can detect anomalous process execution, unauthorized file access, or unexpected network connections within your containers.

Kubernetes Security Contexts

Security Contexts in Kubernetes allow you to define privilege and access control settings for a Pod or Container.

You can specify settings like running as a non-root user, dropping Linux capabilities, or configuring SELinux/AppArmor profiles.

apiVersion: v1
kind: Pod
metadata:
  name: secure-pod
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 1000
    fsGroup: 2000
  containers:
  - name: my-container
    image: my-image
    securityContext:
      allowPrivilegeEscalation: false
      capabilities:
        drop: ["ALL"]

Quick Check: Image Security

Which of the following are best practices for securing container images?

Container Security Recap

In this lesson, we covered key aspects of securing containerized applications:

Minimizing image size and using trusted base images.
Applying the principle of least privilege.
Regularly scanning images for vulnerabilities.
Controlling network access with Kubernetes Network Policies.
Managing secrets securely.
Monitoring containers at runtime for suspicious activity.
Enforcing security settings with Kubernetes Security Contexts.

By following these practices, you can significantly enhance the security posture of your Docker and Kubernetes deployments.

Frequently asked questions

Is the “Container Security (Docker/Kubernetes)” lesson free?

Yes — the full text of “Container Security (Docker/Kubernetes)” is free to read here on the web, and the Secure Coding & OWASP Top 10 for Backend course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Secure Coding & OWASP Top 10 for Backend course, upgrade to CoddyKit PRO.

What will I learn in “Container Security (Docker/Kubernetes)”?

Implement secure practices for building, deploying, and managing containerized applications using Docker and Kubernetes, including image scanning and network policies. You practise Secure Coding & OWASP Top 10 for Backend with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Secure Coding & OWASP Top 10 for Backend?

No prior experience is required. Secure Coding & OWASP Top 10 for Backend on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Container Security (Docker/Kubernetes)” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Secure Coding & OWASP Top 10 for Backend lesson?

Yes. Every Secure Coding & OWASP Top 10 for Backend lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

← Back to Secure Coding & OWASP Top 10 for Backend