How to Build a Zero-Trust Kubernetes Cluster Using Cilium, Istio, and Vault

Many Kubernetes deployments rely on perimeter defenses while leaving internal cluster traffic largely unprotected, creating serious lateral movement risks if a single container is compromised. A zero-trust architecture addresses this by enforcing default-deny network policies using Cilium's eBPF-based CNI, blocking all cross-namespace communication unless explicitly permitted. Istio service mesh is layered on top to enforce strict mutual TLS, ensuring every pod-to-pod connection is both encrypted and cryptographically authenticated. Internal dashboards are secured through Identity-Aware Proxies integrated with corporate SSO, eliminating reliance on basic authentication or direct exposure. Dynamic, short-lived database credentials issued via HashiCorp Vault replace static Kubernetes Secrets, reducing the risk of credential theft and limiting the blast radius of any breach.