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Container and Kubernetes vs. Virtual Machine (VM) security

Virtual machines (VMs) and containers have fundamentally different architectures, though they have just enough similarities to cause some confusion. The differences between containers and VMs have very important security ramifications. Both VMs and containers provide isolation to varying degrees, and both enable portability. Virtual machines are completely self-sufficient, have their own operating system, and do not share resources with other virtual machines. Containers share hosts with other containers, complicating the idea of a secure boundary.

Containers and Kubernetes present a different architectural paradigm that requires a different approach to security. The well-established techniques for host-based security don’t port over to containers. Other security techniques from the host or VM domain, such as building network firewalls around a defined perimeter also don’t apply to containers. In addition, a key part of virtual machine security best practices is applying security patches, but patches cannot be applied to a running container — instead, one should update the container image and rebuild the container.

Securing containers requires:

  • Controlling communications between containers
  • Ensuring containers are free of known vulnerabilities
  • Preventing containers from having root access
  • Restricting permissions and access to only what’s needed for the application to function

Kubernetes adds an additional layer of complexity, and it introduces additional potential security risks. Managing Kubernetes configurations and networking policies is crucial to a strong security posture for containerized applications.

In addition, the workflow changes that come with moving to containerized applications makes it important to integrate security throughout the entire life cycle. Security has to be baked-in to the application from the start, beginning with how images and containers are configured. You can’t add security to a containerized application at the end of the development process, right before deployment.

Security in containerized applications requires controlling the source of all components including open source elements, managing configurations, scanning images, and enabling granular role-based access controls. Containers and Kubernetes force a different approach to security, but given their declarative and immutable nature, they do present the opportunity — when properly configured — to build the most secure applications ever created.

Last updated: May-30-2020