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Concepts

Securing Kubernetes Clusters with Network Policies

Andrios Robert

• 1 min read

The cluster is silent until you give it rules. Without them, every pod can talk to every other pod. Kubernetes Network Policies let you break that silence with precision, defining exactly who can connect, and where.

Kubernetes access controls are not optional in production. Exposed services invite attacks. Internal noise increases latency and complicates debugging. By using Kubernetes Network Policies, you can enforce boundaries at the IP and port level directly inside the cluster.

Network Policies work at the namespace and pod selector level. They are declarative. You write YAML that describes allowed ingress and egress traffic. The policy is applied by the cluster’s network plugin. If the plugin supports it, the rules are enforced immediately.

A basic example:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
 name: allow-frontend-to-backend
 namespace: default
spec:
 podSelector:
 matchLabels:
 role: backend
 policyTypes:
 - Ingress
 ingress:
 - from:
 - podSelector:
 matchLabels:
 role: frontend
 ports:
 - protocol: TCP
 port: 8080

This allows only pods labeled role: frontend to talk to pods labeled role: backend on port 8080. All other connections are denied. Without an explicit allow, default behavior becomes deny—enforcing zero-trust network design inside the Kubernetes cluster.

For Kubernetes access security, combine Network Policies with RBAC to control who can edit the rules. Apply policies in all namespaces, including kube-system, to limit internal service exposure. Audit changes. Test connectivity after deployment to confirm enforcement.

Common best practices:

  • Start with a default deny policy.
  • Gradually allow only the traffic you need.
  • Use namespace isolation for multi-team environments.
  • Align Network Policies with service mesh configurations.
  • Keep YAML definitions under version control.

Kubernetes Network Policies give you fine-grained control without touching application code. They reduce risk, improve performance, and create predictable communication paths inside the cluster.

If you need to see Kubernetes access and Network Policies working without the usual setup overhead, run it live on hoop.dev. Connect your cluster, write your policy, and watch it apply in minutes.