Kubernetes comes with a few security tools built-in, like pod security policies and role-based access control. You might be tempted to assume, then, that securing Kubernetes is as simple as using those tools and calling it a day.
But that would be a major mistake. While Kubernetes’s native security functionality can help, keeping a dynamic, complex, multi-layered Kubernetes environment secure requires drawing on an array of additional security tools and strategies.
Keep reading for tips on what a complete Kubernetes security strategy entails, as well as best practices for approaching the various angles of Kubernetes security that you’ll need to manage to keep your environment truly secure.
Native Kubernetes security features
First, let’s make clear what Kubernetes can do natively, from a security perspective:
- Role-based access control, or RBAC, is a built-in Kubernetes feature that lets you regulate access to services within a Kubernetes environment based on roles and identities.
- Pod security policies allow you to restrict various types of behaviors for pods and containers, such as preventing them from running in privileged mode, or requiring them to use a read-only file system.
- By default, Kubernetes segments networks and namespaces in order to provide a degree of isolation. (Although this translates to real security only if you take the necessary steps to enforce isolation using RBAC and pod security policies.)
- Admission controllers check whether an API request within a Kubernetes environment violates a predefined policy, and rejects it if so. Admission controllers are another tool to help prevent unauthorized behavior in a Kubernetes environment; although, like network and namespace segmentation, they are useful only if you configure and enforce them properly.
These features are a start for securing Kubernetes environments. But they are hardly sufficient on their own. They leave open a number of gaps that can be filled only with the help of a third-party intrusion detection system.
After all, Kubernetes itself is designed to be an orchestrator – not a full-fledged security tool – and it requires external help to manage most of the security risks present in a Kubernetes environment.
Best practices for securing Kubernetes with third-party tools
With that reality in mind, let’s walk through the various types of functionality that third-party security tools add to Kubernetes, and explain how to make the most of each one.
One of the central design principles of Kubernetes is declarative management. This means that administrators write configuration files that define how a Kubernetes environment should behave, and Kubernetes then automatically orchestrates the environment to meet those requirements.
In this respect, configuration files can be one of the greatest risks in your Kubernetes environment. Configurations that are insecure due to lack of planning, or because of configuration mistakes or oversights, translate directly into insecure Kubernetes environments.
That’s why it’s critical to use third-party Kubernetes security tools that can automatically run audit checks by parsing configuration files and identifying misconfigurations that could open up security vulnerabilities. These audits should be run against all of the configurations that apply to a Kubernetes environment, ranging from individual container configurations to those that govern resources like RBAC for the Kubernetes dashboard, and everything in between.
Monitoring and anomaly detection
Kubernetes is a complex, multi-layered tool that consists of a variety of different components, such as containers, pods, clusters and so on. Keeping Kubernetes secure requires careful monitoring; not just of each individual component, but of the ways in which those components interact, in order to detect signs of an intrusion.
Effective security monitoring for Kubernetes must be predicated upon the principle of dynamic baselining. In a fast-moving Kubernetes environment, there is no “normal.” The scope and state of the environment changes constantly. Monitoring tools must be able to understand this constant change and identify anomalies within it by monitoring individual components of the environment while also taking a cluster-wide view. They need to be able to analyze the behavior of an environment within the context of the environment’s configurations, in order to distinguish benign activity from true anomalies.
On the surface, managing known vulnerabilities within a Kubernetes cluster might seem simple. Vulnerabilities within Kubernetes itself, or in the code on which containers depend, are announced, and you fix them. Easy enough, right?
Well, not really. In a fast-moving Kubernetes deployment where multiple vulnerabilities arise each day, vulnerability data is helpful only when it can be easily contextualized by security tools that help you quickly understand how a given vulnerability impacts your environment, what the seriousness of the risk is and how to fix it. For example, it’s important to be able to distinguish between a vulnerability that impacts a testing environment and one that poses a threat to production in order to know which priority level to give the vulnerability.
Compliance requirements are unique to each company. Security tools that help meet compliance goals must, therefore, be adaptable, highly customizable and fully automated. Generic compliance checks that validate whether a Kubernetes environment conforms with a security standard like CIS are not sufficient for ensuring that an environment conforms with the specific compliance requirements of a given organization.
Although Kubernetes segments networks by default, segmentation is effective only when it is backed by configurations that reduce interactions between networks and endpoints to the minimum necessary.
For this reason, it’s important to adopt security tools that let you visualize your Kubernetes networks in order to understand interactions between them. In addition, the tools should automatically generate tightened configuration files that enforce isolation between networks.
Response to Kubernetes security incidents should not only be as automated as possible, but should also allow teams to work from within Kubernetes itself to respond to incidents. For example, security tools should kill pods within Kubernetes when necessary, in order to enforce security policies, so that everyone is aware of the action, and the enforcement can be performed using Kubernetes-native tools. This approach makes it possible to centralize incident management and keep all processes within Kubernetes, even when using third-party tools.
While Kubernetes offers a basic built-in security framework, its security features lack many types of functionality. They are only effective when coupled with third-party Kubernetes security tools that can both fill in the gaps and ensure that the security features that Kubernetes itself does offer are properly configured. By all means, use the security functionality that Kubernetes offers, but don’t make the mistake of relying on that functionality alone.