Kubernetes has recently gained popularity as the tool of choice when working with containerised application management, which has led to the Kubernetes clusters being an essential component of the infrastructure and posing security threats that require protection and appropriate actions to safeguard them to stop security threats and the exploitation of vulnerabilities.
This blog will assist you in first identifying the most common security issues and provide the best practices you can follow to safeguard your Kubernetes cluster.
Why is Securing Your Kubernetes Cluster Important?
Security Threats
There are several security threats to a Kubernetes cluster, including:
- Compromised Cluster and Nodes: Attackers with access to the cluster or nodes can obtain sensitive data, cause disruption, or take over the Kubernetes cluster.
- Container Security: Containers operating within a cluster can be compromised, giving an attacker access to the host system.
- Resource Exhaustion: Attackers can launch a denial of service attack by using up all available resources in the cluster.
- Insecure Network Communications: Unsecured network communications between components can result in the exposure of sensitive data, or allow attackers to intercept communications.
- Configuration Mismanagement: Misconfigurations can result in the susceptibility of sensitive data or applications, allowing attackers to gain access to Kubernetes.
- Insecure Image Repositories: Using untrusted or unverified container images from public repositories can introduce security vulnerabilities into the cluster.
- Inadequate Role-Based Access Control (RBAC): RBAC is a vital security feature in Kubernetes, but if not correctly configured, it can result in the exposure of sensitive data or services, or allow attackers to gain access to the cluster.
- Inadequate Network Segmentation: Inadequate network segmentation can permit the exposure of sensitive data or services, or allow attackers to gain access to the cluster.
The Risks of Misconfigured Clusters
Security implications can also develop through misconfigurations in your Kubernetes environment, highlighting the importance of understanding the security implications of each configuration setting and avoiding using default configurations.
Managed v Self Managed Clusters
Managed Kubernetes clusters are a good option for organisations that want to ensure the cluster is secure and easy to manage. Managed Kubernetes services provide a range of security features and administer the underlying infrastructure for you. The security risk of a managed cluster versus a self-managed cluster depends on several factors.
Here are a few key differences to consider:
Managed Clusters:
- Ease of configuration: Managed clusters are often simpler to set up and configure than self-managed clusters, lowering the risk of incorrect configuration or human error.
- The security of managed resources within a cluster becomes the responsibility of a cloud-based security-focused team, who provides a more trustworthy level of skill and knowledge about the most recent security risks and best practices.
- Reduced workload: With a managed cluster, the provider takes responsibility for the bulk of the security workload, which lessens the workload on engineers administering the Kubernetes cluster.
Self-Managed Clusters:
- A self-managed cluster gives you more control over the security setup, enabling you to make tailored modifications or add extra security measures.
- Additional responsibilities: This heightened control, however, also entails more obligations. Self-managed clusters need a greater degree of skill and awareness because the end user is in charge of all security-related tasks, from initial configuration to continuous maintenance.
- Misconfigurations that could occur: Managing the cluster by oneself increases the potential of configuration errors or security breaches, which could lead to security flaws.
Overall, a managed cluster can offer more security benefits, but with reduced control. A self-managed cluster can provide more control but requires more expertise and effort to maintain the same level of security. The choice between the two will depend on your specific needs and risk tolerance.
Best Practices for Hardening Your Cluster
Here are some best practices for securing your Kubernetes environment:
Cluster Level Actions:
- Use Strong Authentication and Authorisation: Implement strong authentication and authorisation mechanisms to prevent unwanted access to your cluster and its resources, and to stop prohibited access.
- Implement Role-Based Access Control (RBAC): Develop RBAC policies for different roles in your cluster and enforce them using RoleBindings to control who can access what in your environment.
- Use Network Segmentation: Aim to separate your network based on the required security level to assist in isolating and protecting your most crucial workloads and resources.
- Encrypt Communications with TLS: Transport Layer Security (TLS) encrypts all communication between components within the cluster, securing access to sensitive information and reducing the risk of data breaches.
- Enable Auditing: Kubernetes provides built-in auditing to track and record all cluster-related events, assisting in detecting and investigating security incidents.
- Monitoring: Monitoring the cluster allows for the proactive detection of security incidents and identifying abnormal trends in usage and behaviour. To help you understand what’s happening in your environment, extract meaningful information from the system and pod logs. Identifying security issues in Kubernetes can occur using several monitoring tools, including Sysdig, Aqua Security, StackRox, and Falco.
- Alerting: Implementing alerting will benefit the organisation by providing a mechanism for communicating any security breaches to the appropriate individuals. Using custom alerting can also be utilised using Kubernetes APIs and programming languages like Go, Python, or JavaScript. Adopting alerting rules in Prometheus Alert Manager that will send out alerts based on specific conditions or incidents, can also be used.
- Use Managed Clusters: Managed Kubernetes clusters provide security features and manage the underlying infrastructure, making it easier to secure your Kubernetes environment and focus on application development.
- Stay Up-to-Date: Stay informed about the latest security threats and vulnerabilities via subscribing to security-related mailing lists and blogs such as the Kubernetes Security Announcements and the Kubernetes Blog to keep your cluster updated with the latest patches and security fixes.
- The CIS Benchmarks for Kubernetes provide a helpful framework for hardening your environment, but automation is necessary to ensure consistent adherence to best practices. Kube-Bench is a tool that checks compliance with the Kubernetes benchmark recommendations for security.
Container or Pod Level Actions:
- Admission Controller: Implement a dynamic admission controller and implement risk-based policies in your CI/CD pipeline to prevent high-risk misconfigurations from entering production. As of version 1.25, Kubernetes has a built-in Pod Security admission controller that can enforce Pod Security Standards.
- Pod Security: The Pod Security Standards have three policies that range from highly permissive to highly restrictive, users are predominantly advocated to employ the restricted policy that follows best practices.
- Image Scanning: Image scanning ensures that images are adequately checked for security flaws, which helps to lower security risks when used in conjunction with CI/CD pipeline. Using “Distroless” images, which include only the application and its dependencies, as well as Trivy and Clair are popular solutions for image scanning and image security, within Kubernetes.
- Additional Tools and Technologies: Third-party security tools like OPA and Kubernetes security solutions like Falco, AppArmor, and Seccomp can add an extra layer of security to the cluster.
- AppArmor and Seccomp are Linux security modules that limit the capabilities of a process and restrict system calls, respectively.
- Falco is a behavioural activity monitoring tool that detects abnormal activity in real-time.
- Styra OPA is a policy-as-code framework that integrates with Kubernetes to enforce policy decisions.
Image Level Actions:
- Use Trusted Container Images: Only use trusted container images from verified sources to prevent introducing security vulnerabilities into your cluster.
- Sign and Verify Container Images: Image signing and verification prevents malicious images from being executed, which can result in data breaches or harmful access to sensitive information.
Conclusion
Getting to know the security risks that Kubernetes faces and being able to follow the best practices outlined in this blog will bring you one step closer to ensuring the security of a Kubernetes environment, allowing your organisation to focus on its core business with greater confidence in the state of the Kubernetes infrastructure and the reduced risks it poses to potential disruptions or data loss.