Containerization technologies like Docker and Kubernetes have revolutionized the way modern applications are developed, deployed and scaled in the cloud. Containers provide a lightweight, agile and consistent way to help developers quick-build-deploy applications. But at the same time they bring their own security challenges. Containers are subject to threats that can be exploited through compromised images, unpatched vulnerabilities or misconfigurations. Security in the cloud is one of those things that goes beyond simply deploying applications securely and protecting sensitive data; it extends to your underlying container host.

In this article, we will look at the best measures to provide security of containers in the cloud based on two popular containerization platforms – Docker and Kubernetes.

Understanding Container Security

We also know that containers are a unit for packaging applications and their dependencies so they run the same, regardless of where existing in whatever hardware you have. Containers share the underlying operating system (OS) kernel, but their isolation means they do not offer as strong a level of separation compared with VMs and therefore security remains important at every layer.

With containers being dynamically orchestrated and scaled as needed in a cloud environment, the security problem can even get more tangled. This involves applying security best practices across all stages of the container lifecycle — image creation/development to runtime/orchestration.

Docker security best practices

Docker is one of the leading platforms for containerization. Having secured Docker containers is fundamental as to avoid any vulnerabilities through which attackers should exploit. Best Practices for Securing Docker

1. Use Trusted Base Images

The base image forms the basis of any container. Establish a secure, trusted base image A strong start with your dependencies ensures you are not already inheriting vulnerabilities.

• Prefer using Docker Hub official images or other maintained and regularly updated sources for security.
• Stop using big images with vendor software that may open up an attack vector.
• Scan base images for vulnerabilities as a best practice such as Clair, Trivy, Docker Security Scanning.

2. Minimize the Attack Surface

Minimize attack surface by making your containers as lightweight possible, avoiding excess unnecessary packages, services and libraries.

• Use more minimal base images like Alpine or Distroless, which contain less packages out of the box.
• A single application should install only what it needs to run no more.
• Prune the container image from any unnecessary files, tools and library not in use.

3. Implement Least Privilege

This can be huge risk for hackers in case of a breach, DO NOT RUN Containers with more privileges than required by them.

• Run containers as non-root user Docker containers are run as root by default and if an attacker were able to compromise them, it could have disastrous security consequences. In the Dockerfile, create a user and give required permissions.
• Remap container IDs using Docker user namespace with remapping of the users (UIDs) to non-root on host.
• Restrict what a container can do at the kernel level using capabilities—this will limit access to resources

4. DCT is the way to go with Docker Development Trust.

Docker Content Trust provides a means to assure the integrity of container images.

• Turn DCT on to only pull signed and trusted images. This is an extra step to ensure that the images are authentic.
• Machine Meaning Sign an image before you push it to a registry, using the docker trust command.

5. Continuously Scan for Flaws

Your application in a container will be only as secure as the images or libraries used by your Docker containers.

• Incorporate automatic vulnerability scanning in your CI/CD pipeline Aqua Security, Twistlock and Anchore can be applied to detect vulnerabilities and automatically address them even before the containers are deployed.
• Keep security patches updated and keep your base images up-to-date, so that vulnerabilities are patched in a timely manner.

6. Network isolated Containers

Skillful network segmentation prevents containers from talking to services they are not concerned with, which reduces the surface area of attacks.

• Leverage Docker Containers with User-defined Networks to achieve separation of containers unless the need for connectivity between them.
• Use firewall rules to restrict traffic between containers and external networks.
• Encrypt all the data in motion, wherever possible such as secure communication between services should be TLS.

7. Implement Secrets Management

Using sensitive information like API keys, passwords and tokens should be handled securely in container security.

• Do not hardcode secrets into your container images or store them in environment variables.
• Utilize Docker secret management to securely pass in sensitive information into containers when execute the container.
• Enables integration with secret management tools like HashiCorp Vault, AWS Secrets Manager, or Kubernetes secrets for managing secure storage and distribution of application login credentials.

Tips for securing Kubernetes

Kubernetes is one of the favourite and well known container orchestration platforms, it comes with a complete stack where you can use this resource in production to run / scale your applications. That said, the complexity of Kubernetes introduces specific security challenges. Here are few best practices for securing your k8s clusters:

1. Secure the Kubernetes API

• Kubernetes allows for Role-Based Access Control (RBAC) which can be used to restrict the access on Kubernetes API, per user role. Granular user / services specific authorization rules
• Remember to audit logging on enabling it will allow you to monitor API access ensuring there is no suspicious activity happening.
• All communication between the API server, nodes, and other services inside a kubernetes cluster should be encrypted by using TLS encryption.

2. Enable Pod Security Policies

Pod Security Policies (PSPs) restrict what a pod can do, minimizing opportunities for potential vulnerabilities.

• Use PSPs to specify which pod permissions should be enforced (for example, whether a pod can run as root or if it is allowed access to the host network). PSPs can also control the copying files from and writing to running containers or accessing host file system, as well as mounting directories of confidentiality sensitive.
• Define which pods are allowed to talk to each other using network policies. Leverage Kubernetes NaturalPolicy for allowing only specific namespaces or IP ranges to be communicated with.

3. Use Namespaces for Isolation

Namespaces are a way to provide a scope of isolation within one Kubernetes environment. Namespaces allow you to segment workloads for specific security policy enforcement.

• Namespace your resources to isolate them by environment (production vs. development) or team (frontend, backend).
• Resource quotas and network policies should be used to minimize the surface area of each namespace, so one workload does not affect another.

4. Manage Secrets Properly

While Kubernetes offers a native secret management feature, it needs to be used in a secure manner.

• Store sensitive information (i.e., database credentials, API keys) in a Kubernetes Secrets Do NOT store secrets in plain-text configuration files.
• Secrets were encrypted at rest. This means being able to easily enable encryption for secrets using the built-in mechanism available in Kubernetes itself.
• Leverage open-sourced or enterprise vaults like HashiCorp Vault, Azure Key Vault, AWS Secrets Manager for advanced secret management capabilities.

5. Restricting Pod Permissions and Capabilities

Kubernetes gives you control over access and permissions for Pods, similar to Docker.

• Set No Privilege Escalation to your pod context for those times when you need run pods, without the default falborsand risk of running it with an elevated privilage.
• Restrict system calls and operations that containers can execute using seccomp + AppArmor profiles
• Make the filesystem as read-only for Pod and ReadOnlyRootFilesystem=true helps to set it so that root File System is not writable by any applications inside the pod.

6. Enable Runtime Security Monitoring

It is essential to have continuous runtime monitoring because even if you implemented best practices and scanned your containers at the build time, deployed it using a secure image registry service like Harbot, there are still chances of security incidents.

• Monitor the behavior of containers and discover anomalies at runtime with Kubernetes-native tools like Falco or third-party solutions such as Sysdig & Aqua Security.
• Configure alerts for anomalies, eg change in privileges of the user or process, file system changes and unusual network communications etc.

7. Continuous Vulnerability Scanning and Patching:

As Kubernetes clusters are dynamic service environments in which containers constantly deploy and scale. Hackers look for open ports and unpatched services to break into, so vulnerability scanning at regular intervals something as long ago as last Tuesday may have become a new zero-day exploit today—even when the traffic is immaterial just background video feeds—or population inapposite certainly does not mean game over: you MUST implement weekly patching here and everyhwere defensive wise.

• Deploy recurring vulnerability scanning of your container images and the Kubernetes environment itself. Scan for misconfigurations and weaknesses using tools like Kube-hunter.
• Keep Kubernetes always updated to the latest stable release version in order avoid known vulnerabilities.

8. Leverage Image Admission Controllers

To restrict what container images can be deployed to your cluster, Kubernetes provides admission controllers that allow you enforce policies.

• Admission controllers such as Gatekeeper or OPA (Open Policy Agent) can be used to have strict security policies in place, like limiting images from trusted registries only or ensuring that the deployment goes through a series of image scans.
• Introduce image signing for verification of the root and leaf chains to have guarantee security hardening across container images.

Conclusion

In the cloud, container security is a must-have in order to ensure your high-end and modern cloud-native applications are securely processed. Docker and Kubernetes are one such tools which helps to deploy as well manage containers, but it brings a lot of security caveats with them. Adhere to best practices such as using trusted images, enforcing least privilege security mechanisms and leveraging namespace isolation (multitenancy), securing the Kubernetes API server itself and properly managing secrets for a much stronger liklihood that your cloud infrastructure be breach free.

Given the rise in popularity of containers with cloud environments, continuous monitoring, vulnerability scanning and regular patching are a few others. How to securely exploit the benefits of containers in Kubernetes is a final vital question, and through adopting appropriate security practices organizations could utilize all capabilities without worrying about protecting their applications and data from emerging threats.