Securing API Access in Kubernetes with Network Policies and a Proxy

The API gateway was wide open, and the Kubernetes cluster whispered every request through unguarded channels. That’s when the audit began to bite. Misconfigured ingress rules, no namespace isolation, and traffic patterns flowing unchecked. Every packet was an invitation.

Kubernetes Network Policies exist to cut those invitations short. They define which pods can speak to each other, and which cannot. With them, you can lock down lateral movement, restrict external calls, and build a map of allowed connections inside the cluster.

To secure API access through a proxy, first set a default-deny policy. This stops all traffic between pods unless explicitly allowed. Then, create rules that whitelist only the proxy and the upstream services it must reach. Apply these policies per namespace to prevent noisy workloads from touching sensitive endpoints.

Use labels to match pod selectors in your NetworkPolicy manifests. Make ingress rules tight, specifying allowed ports and sources. Do the same for egress, ensuring requests never leave for unexpected destinations. If your API proxy handles authentication and routing, the proxy should be the sole ingress path, with policies blocking direct calls to backend pods.

Audit with kubectl describe networkpolicy and run network policy tests in staging. Probe with tools like netpol to verify enforcement. Combine this with least privilege access at the RBAC level, and you have clean, controlled communication without loose ends.

When Kubernetes Network Policies, secure API access controls, and a proxy join forces, you cut the attack surface to the bone. You own the flow of data, not the other way around.

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