Container security best practices (without the toil)

In the grand edifice of modern cloud software systems, Docker containers have become the bricks forming the foundation, holding everything up from microservices to AI and more. But what if the bricks came to the building site with cracks) already in them?

Traditional base container images can harbor hundreds of security vulnerabilities. Manual inspection and patching generally can't keep pace with emerging security threats, especially as new cracks form faster than you can find them.

The solution isn't reactive firefighting or more tracking tools for all your bugs. It's a shift to secure-by-default practices: minimal base images, continuous vulnerability remediation, and provenance-driven supply chain security. This guide will take you through actionable container security best practices you can implement today to reduce risk, maintain compliance, and ensure every brick in your infrastructure is solid from build to runtime.

The container security challenge: Why traditional approaches are failing

Most security incidents in containerized environments don't stem from a single instance of careless oversight in your development lifecycle. They result from a system filled with gaps: fragmented processes, reactive approaches, and misaligned tooling. It’s as if you’re building your structure with bricks that came riddled with cracks. They may multiply faster than you can patch them, compromising everything you’ve built on top. Understanding these challenges is the first step toward replacing the foundation entirely.

Common obstacles include:

• Tool sprawl creates inconsistent coverage. When security is spread across disparate tools, gaps emerge between scanning, policy enforcement, and runtime protection. Teams manage multiple dashboards, each with its own data model and alert format, making it difficult to get a unified view of risk.

• Fragmented processes between dev, security, and ops. Containers allow dev teams to move fast, but security processes built for monolithic systems can't keep up, creating friction and delays. Developers push to production on Friday afternoon. Security fires off a Slack message Monday morning: “There’s a critical CVE (Common Vulnerability and Exposure), a rollback is required.” Operations gets the 2 AM page to pull everything down while customers hit error screens. Deploys stall, customer trust erodes, and the next release gets even more scrutiny and delay.

• Visibility gaps across container lifecycles. Without clear insight from build to runtime, teams struggle to track which images are running where and whether they're still secure. An image that was safe last week might have a critical CVE today, but you can’t remediate images that you don’t know have been deployed.

• Reactive remediation only after vulnerabilities hit production. Detecting CVEs post-deployment means scrambling to patch live systems, often with downtime and risk. This reactive approach can create firefighting instead of proactive security solutions. Every reactive fire drill burns hours of expensive engineering time, delays roadmap work, and trains your team that security is something that happens to them, not something they control.

• Compliance complexity for regulated industries. Meeting standards like FIPS, STIG, or FedRAMP requires continuous verification, documentation, and auditable processes that manual workflows can't sustain. Auditors expect evidence of secure practices at every stage, and producing that evidence manually is time-consuming and error-prone.

The good news is that you can solve these challenges with the right approach and tooling. The key is shifting from reactive, manual processes to automated, secure-by-default practices. When you build with good bricks from the beginning, you can move at the speed and scale modern development demands.

4 best practices for securing containers

At Chainguard, we use Container Hardening Priorities (CHPs) as a framework for our container security. CHPs (pronounced “chips”) provides a structured and auditable framework for evaluating and implementing container security best practices. Rather than treating security as a checklist, CHPs organize practices into four pillars: Minimalism, Provenance, Configuration & Metadata, and Vulnerabilities. This makes it easier to prioritize and adopt practices systematically. CHPs even comes with a scorer you can integrate into your project to see how well you’ve implemented these practices.

Minimalism

Minimalism reduces the attack surface by removing unnecessary components from your Docker containers. The fewer packages and dependencies a container image has, the fewer vulnerabilities it can introduce. Minimalism also extends beyond base images, covering permissions, runtime configurations, and tailoring images for specialized workloads like AI/ML. These practices create a stronger foundation for compliance and operational simplicity.

Always use verified, minimal base images

Start with the smallest possible base image. Traditional distros like Debian or Ubuntu include hundreds of packages you don't need, each a potential security risk. Minimal images (like Alpine or distroless) strip away unnecessary components, giving you less attack surface.

Even better: use Chainguard’s base images that are purpose-built for security. Chainguard provides minimal, secure-by-default base images with zero known CVEs at the time of publishing. They're rebuilt daily to incorporate the latest patches, so you're not waiting weeks or months for upstream distro maintainers to publish updates. A typical Ubuntu base image might contain 200+ packages and dozens of known CVEs. A Chainguard equivalent contains only what's necessary to run your application.

Implement least privilege and runtime restrictions

Docker containers should never run as root unless absolutely necessary. Configure your images to use non-root users by default. In Kubernetes, enforce security contexts that drop unnecessary Linux capabilities, turn off privilege escalation, and set read-only root filesystems. If the container does have an unpatched CVE, if you’re not running it as root, then a hacker won’t be able to gain unauthorized access to another privileged node in your host system.

Automate vulnerability remediation

This shift from reactive to proactive remediation is critical for reducing your Docker container's exposure window and improving DevOps productivity by eliminating constant context-switching to handle security alerts. Manual patching is slow, error-prone, and doesn't scale. Every CVE disclosure triggers a cascade: someone needs to identify affected images, prioritize severity, coordinate patches across teams, rebuild containers, test for regressions, and redeploy, potentially costing you days of software development time.

Use a platform that automatically rebuilds and patches images when new vulnerabilities are disclosed. Chainguard Images, for example, come with CVE remediation SLAs and daily rebuilds, so your images stay current without manual intervention.

Choose compliance-ready images for regulated workloads

If you operate in a regulated industry with sensitive data, generic container images won't cut it. You will need pictures that meet STIG baselines, FIPS 140-2/140-3 validation, or CIS Benchmark requirements. Chainguard offers STIG-hardened and FIPS-validated images designed for government and enterprise compliance requirements. These images are pre-configured to meet strict security controls, saving you weeks of manual hardening and continuous auditing. Compliance means proving your security posture to auditors, customers, and partners. Good documentation makes audits faster and less painful.

Reduce vulnerabilities in specialized workloads

AI and machine learning workloads present unique security challenges. They often rely on complex dependency trees (TensorFlow, PyTorch, CUDA libraries) that can introduce hundreds of CVEs, and standard security approaches struggle to keep up.

Chainguard provides hardened images for AI/ML workloads, pre-configured with popular frameworks but stripped of unnecessary packages. This minimizes vulnerabilities while maintaining the performance and compatibility these workloads demand. The same principle applies to other specialized workloads. Whether running databases, message queues, or web servers, Chainguard has purpose-built minimal images tailored to your specific use case that provide better security than general-purpose base images bloated with unused components.

Provenance

Provenance is the ability to verify an image's lineage: where it came from, who built it, and whether it's been tampered with. It is foundational to supply chain security. If you can't prove it’s the trusted image, you can't prove compliance.

Sign and verify all container images

Signature verification should happen at multiple stages. Sign images when they're built in CI. Verify signatures before pushing to production registries. Use admission controllers to verify signatures again before Docker containers are allowed to run. This defense-in-depth approach prevents tampered or unauthorized images from ever reaching your infrastructure.

But if you want this managed, Chainguard images are signed by default with verifiable provenance metadata. This means you can cryptographically verify the origin and integrity of every image without additional configuration: no manual setup, no separate tooling, just built-in trust.

Maintain a comprehensive SBOM for every image

A Software Bill of Materials (SBOM) is a complete inventory of all components, libraries, and dependencies in a container image. SBOMs are essential for vulnerability management, compliance, and incident response. If a new CVE is disclosed in a widely used library, an SBOM lets you instantly identify which images are affected. When a major vulnerability like Log4Shell is disclosed, teams with comprehensive SBOMs can identify affected systems in minutes instead of days. This speed can be the difference between minor incidents and major security breaches.

Chainguard Images include a complete, attested SBOM for every image. These SBOMs are generated and signed at build time so that you can trust the data. No need to bolt on third-party SBOM tools or maintain separate inventories.

Enforce immutable infrastructure practices

Immutable infrastructure means never modifying running containers. Once a container is deployed, it stays exactly as it was built. If you need to make a change, you create a new image and redeploy. This approach prevents configuration drift, simplifies rollback, and makes auditing straightforward. You always know exactly what's running because it matches the image you tested and signed. With immutable containers, every deployment is identical and reproducible, eliminating entire classes of "works on my machine" problems.

Configuration & metadata

Configuration and metadata cover the policies, controls, and settings that govern how containers run and interact with other systems. Insecure defaults, weak secrets management, or poorly hardened registries can undo the benefits of minimalism and provenance.

Practices here are about enforcing standards, securing metadata, and locking down orchestration environments.

Use policy as code to enforce security standards

Policy as code lets you define security and operational rules in version-controlled, testable formats. Tools like Open Policy Agent (OPA) or Kyverno allow you to enforce policies such as "no containers running as root" or "all images must be signed" automatically at admission time. By codifying policies, you eliminate manual checks and ensure consistent enforcement across all environments. Policies become auditable, repeatable, and scalable, a critical practice for enterprises managing hundreds or thousands of workloads.

Policy as code also enables gradual rollout and testing. You can start by running policies in audit mode to identify violations without blocking deployments, then switch to enforcement once your teams have addressed the issues. This approach reduces friction while improving security posture.

Secure secrets management in containers

Say it three times with me: “Never hard-code secrets into container images or pass them as environment variables in plaintext!” Use dedicated secrets management tools like HashiCorp Vault, AWS Secrets Manager, or Kubernetes Secrets. Mount secrets as files or inject them at runtime, and rotate them regularly. Proper secrets management prevents accidental leaks and limits the damage if a container is compromised.

Harden your container registries and orchestration environment

Your container registry is a critical piece of infrastructure. If an attacker gains access, they can inject malware or steal proprietary code. Enforce role-based access control (RBAC), enable audit logging, and require signed images for all pushes.

Similarly, harden your Kubernetes or orchestration platform. Disable unnecessary APIs, enforce network policies, enable admission controllers, and regularly audit RBAC configurations. A secure registry and orchestration layer are the foundation for everything else.

Network segmentation is particularly important. Use network security policies to restrict which pods can communicate with each other in your container environment. Default to deny-all policies, then explicitly allow only the connections your applications need, to limit lateral movement if an attacker compromises a single container.

Vulnerability prevention & response

Vulnerabilities are the continuously emerging flaws in source code and dependencies that attackers exploit. No matter how "secure" an image appears today, new CVEs are discovered daily, making vulnerability management an ongoing responsibility.

Practices in this pillar focus on proactive scanning and continuous monitoring to identify and remediate risks quickly.

Scan images at every stage of the pipeline

Don't wait until production to discover vulnerabilities. Integrate image scanning for vulnerabilities into your CI/CD pipeline in real time so that every image is scanned before it's pushed to a registry and again before deployment.

Use tools that understand the context of your images and provide actionable remediation guidance, not just a list of CVEs. Prioritize vulnerabilities based on exploitability, reachability, and whether a fix is available.

Scan continuously, not just when images are built. New vulnerabilities are disclosed daily, so images that were clean last week might have critical CVEs today. Continuous scanning across your entire registry ensures you can identify and remediate issues as soon as they're discovered, not weeks or months later.

Continuously monitor and audit runtime activity

Security doesn't stop once a container is deployed. Runtime security tools monitor container behavior for anomalies like unexpected network connections, malicious code from file modifications, or privilege escalations.

Use runtime detection tools (like Falco or Sysdig) to alert about suspicious activity and enforce policies that prevent unauthorized behavior. Pair this with centralized logging and audit trails to investigate incidents. Runtime monitoring also helps you refine your security policies. By observing normal application behavior, you can tighten restrictions and create more targeted policies that reduce risk without breaking functionality.

How Chainguard simplifies container security

While any organization can attempt to implement these best practices manually, Chainguard's platform is designed to make them automatic, consistent, and continuous. Instead of stitching together fragmented tools and processes, Chainguard provides a unified approach to supply chain security.

Key features include:

• Secure-by-default, minimal base images with zero known CVEs. Start with the smallest possible attack surface and eliminate hundreds of vulnerabilities in traditional base images.

• Daily automated rebuilds and CVE SLAs for rapid vulnerability remediation. New vulnerabilities are patched and images are rebuilt automatically, so you never wait for manual updates.

• Signed images with built-in provenance and SBOMs for every artifact. Trust and transparency are built into every image, with cryptographic verification and complete dependency inventories included by default.

• Compliance-ready images meeting STIG, FIPS, and CIS Benchmarks. Reduce months of manual hardening with pre-configured images designed to meet the strictest regulatory requirements.

• Complete supply chain transparency with verifiable build processes. Every image includes attestations and builds metadata, so you can prove exactly how it was created.

• Seamless integration into existing CI/CD workflows for shift-left security. Drop-in replacements for standard base images mean you can start securing your supply chain without rewriting your pipelines.

Ready to see how Chainguard can simplify your container security? Talk to an expert or take the course to learn more.