Container Security Best Practices

Containerized applications have become the standard for building and deploying software, offering unmatched speed and scalability. But this flexibility comes with a new set of security challenges. A single misconfigured container or a vulnerability in a base image can create an entry point for attackers, potentially compromising your entire cloud environment. Simply put, if you're not actively managing container security, you're leaving a door wide open.

Looking for a fast way to surface misconfigurations and vulnerabilities? Aikido Security's container image scanning can be seamlessly integrated into your workflow, helping you strengthen security from the start.

Core Principles of Container Security

Securing containers isn't a one-time task; it's a continuous process that spans the entire application lifecycle. Think of it as a DevSecOps approach, where security is integrated from the earliest stages of development through to production and beyond. The goal is to shift security left, finding and fixing issues before they ever reach a live environment. For context on why this matters, consider that over 60% of organizations have experienced a container security incident, as reported by Red Hat's State of Kubernetes Security.

This involves three key areas:

• Securing the build pipeline: Protecting container images and the software supply chain, a best practice recommended by the National Institute of Standards and Technology (NIST).
• Securing the configuration and deployment: Ensuring containers and their orchestrators are configured correctly.
• Securing the runtime environment: Monitoring and protecting live containers.

For a concrete deep dive into implementation, check out our cluster post on Container Security — The Complete Guide.

Best Practices for Securing the Build Pipeline

The security of your containers starts long before they are deployed. It begins with the images you use and the code you write. For a step-by-step checklist and more actionable advice, don’t miss Container Security Best Practices & Checklist or the practical perspective in Cloud Container Security: Protecting Kubernetes and Beyond.

1. Use Minimal and Trusted Base Images

Every piece of software in a container image adds to its attack surface. Using a large, general-purpose base image like the full Ubuntu OS brings in countless libraries and binaries that your application likely doesn't need, many of which may have known vulnerabilities.

• Choose minimal images: Opt for "distroless" or "alpine" base images. Distroless images contain only your application and its runtime dependencies, nothing else. Alpine Linux is a much smaller alternative to full-featured distributions, significantly reducing the attack surface.
• Use trusted sources: Pull images only from reputable registries like Docker Hub's official images or trusted internal registries. Avoid using public images from unknown publishers, as they could contain malicious code.
• Pin image versions: Instead of using the :latest tag, specify an exact version (e.g., node:18.17.1-alpine). This prevents unexpected breaking changes or new vulnerabilities from being introduced into your builds automatically.

If you want to automate these checks, consider using our container image scanning solution to spot issues early.

2. Scan Images for Vulnerabilities

Container images are composed of layers, including an operating system, system libraries, and application dependencies. A vulnerability in any of these layers can be exploited. This is where container image vulnerability scanning becomes critical.

• Integrate scanning into CI/CD: Automate vulnerability scans every time a new image is built. This ensures that security checks are a standard part of your development workflow.
• Scan for more than just OS packages: Effective scanning tools check for vulnerabilities in OS packages (like apt or yum) and application dependencies (like npm, pip, or Maven).
• Block vulnerable builds: Configure your CI/CD pipeline to fail the build if high-severity vulnerabilities are discovered. This enforces a baseline security standard before code is even merged.

Learn more about the latest tools for this purpose by visiting our write-up on Top Container Scanning Tools in 2025.

3. Manage Application Dependencies (SCA)

Your own code relies on dozens, if not hundreds, of open-source packages. A single vulnerable dependency can compromise your entire application. Software Composition Analysis (SCA) helps you find and manage these risks. For actionable tools, explore our page on open-source dependency scanning (SCA).

• Generate a Software Bill of Materials (SBOM): An SBOM is a complete inventory of every component in your software. This is crucial for tracking dependencies and quickly identifying the impact of a newly discovered vulnerability.
• Check for outdated licenses: SCA tools can also scan for non-compliant or risky open-source licenses, helping you avoid legal issues.
• Prioritize fixes: Focus on vulnerabilities that are actually exploitable. Modern tools can analyze whether a vulnerable function is being called in your code, helping you prioritize real threats over theoretical ones.

To streamline both vulnerability and misconfiguration detection (including IaC and secrets), you can leverage Aikido Security's CSPM solution for full-stack protection across your cloud workloads.

Best Practices for Deployment and Configuration

A secure image can still be compromised if it's deployed with weak configurations. Securing the environment where your containers run is just as important as securing the containers themselves.

1. Enforce the Principle of Least Privilege

Containers should only have the permissions they absolutely need to function. Running containers with excessive privileges is one of the most common and dangerous misconfigurations.

• Don't run containers as root: By default, containers run as the root user. This is a major risk. If an attacker gains control of the container, they have root access. Use the USER instruction in your Dockerfile to specify a non-root user.
• Limit kernel capabilities: Docker's default settings grant containers a range of kernel capabilities. Drop all unnecessary capabilities using the --cap-drop=all flag and add back only those that are essential (--cap-add=...).
• Use read-only filesystems: If a container doesn't need to write data to its filesystem, run it in read-only mode (--read-only). This prevents attackers from modifying files or installing malware.

For more configuration pitfalls and remediation strategies, our guide on Harden Your Containers with Aikido x Root covers common mistakes and practical fixes.

2. Secure Your Container Orchestrator (Kubernetes & Docker)

Orchestration platforms like Kubernetes and Docker Swarm introduce their own layer of configuration and potential risk.

• Use network policies: In Kubernetes, network policies act as a firewall for pods. By default, all pods can communicate with each other. Use network policies to restrict traffic between pods, allowing only necessary connections.
• Manage secrets properly: Never hardcode secrets like API keys, passwords, or certificates in your container images or environment variables. Use your orchestrator's built-in secrets management tools (e.g., Kubernetes Secrets) or a dedicated solution like HashiCorp Vault.
• Enable role-based access control (RBAC): For Kubernetes, ensure RBAC is enabled to control who can access the Kubernetes API and what permissions they have. Grant permissions based on the principle of least privilege.

Improving your cloud configuration is a continuous effort. Tools for cloud security posture management can automate the detection of misconfigurations across your entire cloud environment, giving you a clear path to remediation. Curious to see how it works? Try out Aikido Security to get a handle on your cloud security posture.

If you’re looking for a side-by-side look at orchestration security, you might find Docker & Kubernetes Container Security Explained especially useful.

Runtime Security and Monitoring

Once your containers are running, the job isn't over. You need to monitor them for threats and anomalous behavior. According to research from the National Institute of Standards and Technology, runtime monitoring is a key component of effective container security strategies.

1. Monitor for Runtime Threats

Runtime security involves detecting and responding to threats in real time. This can include an attacker exploiting a zero-day vulnerability or a container behaving in an unexpected way.

• Track network activity: Monitor network connections to and from your containers. Look for connections to suspicious IP addresses or unusual data transfer patterns, as highlighted by the Center for Internet Security's best practices.
• Monitor file system access: Keep an eye on file integrity. Unexpected changes to critical system files could be a sign of a compromise.
• Log everything: Centralize logs from your containers, hosts, and orchestrator. This provides the visibility needed to investigate security incidents when they occur.

For insight into the practical realities of runtime threats, check out our Container Scanning & Vulnerability Management article, which outlines how regular scanning and monitoring work hand-in-hand.

A Practical Container Security Checklist

Here is a simple checklist to help you implement these container security best practices.

Conclusion

Container security is a critical part of modern software development. By adopting a DevSecOps mindset and integrating security into every stage of the lifecycle, you can build, deploy, and run applications with confidence. Start with securing your base images, automate vulnerability scanning, and enforce secure configurations. This proactive approach will protect your applications and keep your development teams moving fast.

To see how automated scanning, vulnerability management, and compliance checks can fit seamlessly into your workflow, take a closer look at Aikido Security’s cloud posture management solution.