Kubernetes Security Best Practices Part 2: Network Policies

The blog post discusses the significance of Kubernetes NetworkPolicies in enhancing security by restricting network flow between pods in a Kubernetes cluster. It explains that, by default, all pods can communicate freely, which poses security risks if an attacker gains control of a pod. NetworkPolicies mitigate this risk by allowing administrators to specify connections on the IP address or port level, requiring a Container Network Interface (CNI) that supports them, such as Calico or Cilium. The post outlines the importance of creating a "deny-all" NetworkPolicy to block all traffic initially and then selectively allowing only necessary connections. Best practices also include blocking access to the cloud provider's Metadata API to prevent unauthorized access to sensitive data. The post emphasizes the significance of meaningful naming conventions for NetworkPolicies and provides a detailed example of creating and applying NetworkPolicies to control pod communications. It concludes with a reminder of the steps to effectively implement NetworkPolicies, ensuring the use of a compatible CNI, establishing a deny-all policy, defining allowed connections, and testing the policies for effectiveness.