If you manage containerized applications on a Kubernetes cluster, you’re already aware of its impressive capabilities and flexibility. However, this power also brings significant responsibility—most importantly, the need to secure your cluster and workloads. Overlooking Kubernetes security best practices is like leaving your house keys out in the open. That’s something we want to avoid.
As your dedicated cloud native security partner, I’ve assembled the ultimate Kubernetes security checklist. This goes beyond simply checking boxes; it’s about comprehending and applying layered security measures to greatly minimize your attack surface and strengthen your entire Kubernetes environment. Let’s explore what it takes to achieve a truly secure Kubernetes deployment.
Key Takeaways
- Enforce Least Privilege: Use RBAC and security context settings to ensure users and service accounts have only the permissions necessary for their role. Operate containers as non-root users with a read-only file system.
- Shift Security Left: Analyze your container images for vulnerabilities during the CI/CD pipeline to detect and resolve issues prior to deployment.
- Default Deny Policy: Implement network policies to limit ingress and egress traffic between Pods. Deny all traffic by default and permit only what is required.
- Strengthen the Hosts: Protect your nodes and encrypt confidential data saved in etcd and Kubernetes secrets. Note: Kubernetes Secrets are only Base64 encoded by default; always enable Encryption at Rest using a KMS (Key Management Service) provider.
Layer 1: Fortifying the Foundation With Cluster and Node Hardening
The foundation of security lies in protecting the core infrastructure. Just as a house needs a solid base, your systems require strong underpinnings to remain secure.
- Safeguard the Control Plane: The control plane elements, particularly the API server and etcd, serve as the central intelligence of your Kubernetes cluster. Limit access to these components with a firewall and ensure that all communications, including those between the kubelet and API server, are encrypted with TLS.
- Strengthen the Nodes: Your worker nodes (which execute your workloads) should operate on lightweight Linux distributions, such as Alpine or other minimal images, to reduce the attack surface. Disable any unnecessary services, and routinely update these nodes to address known vulnerabilities.
- Apply Security Updates and Manage Vulnerabilities: This step is essential. Establish a proactive process to keep Kubernetes components, nodes, and all dependencies up to date and patched. Regular updates are a straightforward way to protect against many common exploits.
Layer 2: Controlling Access and Permissions
The principle of least privilege is crucial in this context. Neither humans nor machines should have more permissions than necessary.
- Authentication and Authorization: Use your existing identity provider for user authentication. For authorization within the Kubernetes cluster, rely primarily on role-based access control (RBAC).
- Proper RBAC Implementation: Create detailed roles and role bindings to limit the actions that users and service accounts are allowed to perform within a specific namespace or throughout the cluster. Avoid using default service accounts for application workloads and ensure their permissions are as restrictive as possible. If a service account is breached, its limited RBAC permissions will help contain the damage.
Layer 3: Securing Container Images and the Supply Chain
Before your code reaches the container runtime, it’s essential to ensure that your foundational components are secure. This process is known as securing your supply chain.
- Image and Supply Chain Security: Choose trusted, verified, and minimal container images as your base. Smaller images reduce the attack surface. Whenever possible, opt for “distroless” images.
- Vulnerability Scanning in the CI/CD Pipeline: Incorporate scanning tools into your CI/CD pipeline to automate the identification of known vulnerabilities in your container images prior to deployment. Only deploy images that have been properly scanned and approved.
- Ensure Image Provenance: Utilize image signing to confirm that the container images you deploy are the same ones you created and have not been altered.
Layer 4: Pod and Runtime Security
This layer is dedicated to strengthening the security of your active applications—specifically, the container security measures implemented during deployment and throughout runtime.
- Pod Security: Implement Pod Security Admission (PSA) to enforce Pod Security Standards (PSS). Note that PodSecurityPolicy (PSP) was deprecated in v1.21 and completely removed in v1.25; it should no longer be used. For requirements more granular than PSS, consider third-party policy engines like Kyverno or OPA/Gatekeeper
- Security Context: Set the security context for your pods to run as a non-root user and configure the file system as read-only whenever feasible. Avoid using privileged containers to reduce the risk of privilege escalation attacks.
- Runtime Protections: Leverage tools such as Seccomp (Secure Computing Mode), AppArmor, or SELinux to limit the operations a container runtime can execute on the host Linux system. This is essential for preventing container escapes.
Layer 5: Network and Resource Isolation
Segment your network traffic and resource usage to stop attackers from moving laterally in the event of a breach.
- Network Security with Network Policies: Define how Pods communicate. While “Default Deny” is the gold standard, remember that standard Network Policies do not support DNS-based rules or Layer 7 filtering. For these advanced features, a Service Mesh or a specialized CNI like Cilium is required.
- Resource Management and Isolation: Separate namespaces should be your primary isolation method for different teams or environments, such as production (prod), staging, or development (dev). Apply resource quotas to namespaces to control CPU and memory usage, reducing the risk of a denial-of-service or crypto-mining attack affecting a compromised workload.
Layer 6: Policy Enforcement and Observability
How can you ensure these rules are consistently enforced? You implement policy enforcement and maintain vigilant oversight.
- Admission Controllers and Policy Enforcement: Implement admission controllers (such as the built-in Pod Security Admission or policy-as-code solutions like OPA/Gatekeeper) to apply your security policies whenever a resource is created or modified in the Kubernetes API. These act as a safeguard to prevent insecure configurations from being deployed.
- Logging, Auditing, and Monitoring: Activate and gather audit logs from the Kubernetes API server. It’s essential to thoroughly monitor your cluster’s health, pod lifecycles, and runtime activities to quickly identify and address suspicious actions. This visibility across your entire cloud native environment is crucial for maintaining robust security.
SolarWinds and Your Kubernetes Security Posture
Maintaining a secure Kubernetes environment demands ongoing attention and comprehensive visibility. It’s essential to quickly identify potential issues—such as a misconfigured security context, an excessively permissive RBAC role, or a pod making unusual network requests. This is where a unified observability platform proves invaluable.
SolarWinds® Observability supports a crucial aspect of your Kubernetes security checklist by offering the monitoring and alerting capabilities necessary for continuous oversight and swift incident response.
How SolarWinds Observability Supports You:
- Comprehensive Kubernetes Monitoring: Gain in-depth, real-time insights into the health, performance, and resource consumption of your entire Kubernetes cluster, covering nodes, pods, and container runtime activities. Access a unified dashboard for metrics, traces, and logs.
- Anomaly Detection: With continuous monitoring of your workloads and the container lifecycle, the platform helps detect and alert you to unusual performance or behavior that could signal a security incident overlooked by static analysis tools.
- Accelerated Troubleshooting: When problems occur—whether security-related or otherwise—you receive the necessary context to promptly identify and resolve the issue, greatly reducing the time needed to reestablish a secure security posture.
FAQs
What are Common Container Security Threats and Attacks?
Frequent risks include using outdated or unpatched base images that contain known vulnerabilities (CVEs), as well as running containers with root access or excessive permissions, which increases the risk of privilege escalation. Another significant issue is the insecure management of Kubernetes secrets, where sensitive data may be unintentionally revealed. Additional concerns include container breakouts, where attackers escape the container runtime to reach the host nodes, and supply chain attacks, which introduce malicious code during the application’s lifecycle.
How can I implement network policies to enhance security in Kubernetes?
You implement network policies—Kubernetes resources that set rules for traffic flow—to secure communications. The recommended method is to begin by applying a policy that denies all ingress and egress traffic for Pods within a specific namespace, creating a zero-trust baseline. Then, define separate, highly targeted network policies that specifically permit only the ingress and egress traffic required for your workloads to operate. To further enhance network security, use a CNI like Cilium for Layer 7 visibility or a service mesh to enforce mutual TLS.