In the modern software development landscape, containerization has become the standard for packaging and deploying applications. However, as the use of containers grows, so do concerns about supply chain security. Vulnerabilities hidden within container images can open the door to severe security breaches, leading to compromised systems and data leaks.

To address this, developers and security teams are turning their focus to creating and maintaining clean container images—stripped-down, secure images that minimize risk and enhance supply chain integrity. This article explores why clean container images are revolutionizing supply chain security and how you can implement best practices to safeguard your workflows.

Why Clean Container Images Matter

Container images are often built from multiple layers, with each layer potentially introducing vulnerabilities. Common issues include:

• Unused packages and dependencies that bloat images and increase the attack surface.
• Outdated libraries with known vulnerabilities.
• Hardcoded secrets or sensitive data inadvertently included in the image.
• Misconfigurations that may expose the container to external threats.

These issues not only impact the security of the application but also its performance and scalability. By focusing on clean container images, organizations can:

• Reduce vulnerabilities by eliminating unnecessary components.
• Enhance performance through leaner images.
• Simplify compliance with industry standards and regulations.
• Improve maintainability and streamline CI/CD pipelines.

The Role of Supply Chain Security in Containers

Supply chain security ensures that every component in your software delivery pipeline—tools, libraries, dependencies, and images—is verified and trusted. Containers present unique supply chain challenges, as they often bundle code from numerous sources, including public registries.

Recent high-profile attacks (such as the SolarWinds breach) have highlighted the dangers of insecure software supply chains. Attackers target weak points in the supply chain to insert malicious code, which then spreads downstream.

Clean container images act as a frontline defense in this battle, providing a verified, secure starting point for application deployment.

Best Practices for Creating Clean Container Images

1. Use Minimal Base Images

One of the most effective ways to clean up container images is to start with a minimal base image. Popular options include:

• Alpine Linux (~5MB): A lightweight Linux distribution that reduces the attack surface.
• Distroless Images: Contain only the application and its runtime dependencies—no package manager or shell.

Example:
Instead of using:

FROM ubuntu:latest

Use:

FROM alpine:latest

Or:

FROM gcr.io/distroless/python3

2. Avoid Installing Unnecessary Packages

Each additional package increases the potential for vulnerabilities. Install only what is strictly necessary for the application to function.

Before:

RUN apt-get update && apt-get install -y curl vim git

After:

RUN apt-get update && apt-get install -y curl

3. Regularly Scan Images for Vulnerabilities

Integrate image scanning tools into your CI/CD pipeline to detect known vulnerabilities. Popular tools include:

• Trivy
• Anchore
• Clair
• Docker Scout

These tools can catch issues before the image is deployed, ensuring that only clean and secure images make it to production.

4. Implement Multi-Stage Builds

Multi-stage builds help reduce image size by separating build and runtime environments.

Example:

# Build stage
FROM golang:1.17 AS builder
WORKDIR /app
COPY . .
RUN go build -o myapp

# Final stage
FROM alpine:latest
WORKDIR /app
COPY --from=builder /app/myapp .
ENTRYPOINT ["./myapp"]

This approach ensures that the final image contains only the built application and its runtime dependencies, with no leftover build tools.

5. Manage Secrets Securely

Avoid hardcoding secrets (like API keys or passwords) in container images. Use tools like:

• HashiCorp Vault
• AWS Secrets Manager
• Docker secrets

Example:

docker run -e API_KEY=$(vault read -field=key secret/myapp) myapp:latest

6. Keep Dependencies Up-to-Date

Regularly update the dependencies used in your container images to avoid known vulnerabilities. Use tools like:

• Dependabot
• Renovate
• Snyk

Automating dependency management helps keep your images clean and secure.

7. Employ Container Signing and Verification

Use tools like Cosign or Notary to sign container images, ensuring authenticity and integrity. This helps verify that the images haven’t been tampered with during the delivery process.

Example:

cosign sign myapp:latest
cosign verify myapp:latest

Automating Clean Image Practices in CI/CD Pipelines

Integrating the above practices into CI/CD workflows can help automate clean image creation.

Example CI/CD Workflow (Using GitHub Actions):

name: Build and Push Clean Docker Image

on:
  push:
    branches: [ main ]

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - name: Checkout code
        uses: actions/checkout@v2

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v1

      - name: Build and push Docker image
        uses: docker/build-push-action@v2
        with:
          context: .
          push: true
          tags: myapp:latest

      - name: Scan Docker image for vulnerabilities
        uses: aquasecurity/trivy-action@master
        with:
          image-ref: myapp:latest

      - name: Sign Docker image
        run: cosign sign myapp:latest

This workflow:

• Builds the container using best practices.
• Scans the image for vulnerabilities.
• Signs the final image for verification.

Clean Images and Compliance

Many industries require adherence to strict compliance standards like HIPAA, PCI-DSS, or GDPR. Clean container images help meet these requirements by:

• Reducing the attack surface.
• Ensuring images are built from verified sources.
• Implementing secure configurations by default.

Example:

• Using distroless images for compliance with PCI-DSS.
• Applying strict file permissions within images to meet HIPAA standards.

Challenges in Maintaining Clean Container Images

While clean images offer numerous benefits, challenges include:

• Complex Dependencies: Some applications require large libraries that bloat images.
• Legacy Applications: Older codebases may not support minimal base images.
• Frequent Updates: Constantly updating images to patch vulnerabilities can be resource-intensive.

Overcoming These Challenges

• Use multi-stage builds to separate concerns.
• Leverage automated scanning and dependency management tools.
• Implement immutable infrastructure practices—replace containers rather than patch them.

The Future of Supply Chain Security

With the growing importance of supply chain security, expect to see:

• More advanced container scanning tools with real-time vulnerability detection.
• Wider adoption of software bills of materials (SBOMs) to trace dependencies.
• Stronger emphasis on zero-trust container environments—where every image and layer is verified and isolated.

Conclusion

Clean container images are no longer a luxury—they’re a necessity. As supply chain attacks grow more sophisticated, building and maintaining clean images is one of the most effective ways to protect your software delivery pipeline.

By following best practices—using minimal base images, scanning for vulnerabilities, managing secrets securely, and integrating automated checks into CI/CD—you can create lean, efficient, and secure containers that reduce risk and improve performance.

Start today by auditing your existing container images and adopting these practices. In the ever-evolving world of supply chain security, clean container images are your first line of defense.