Three multi-tenant isolation boundaries of Kubernetes

Kubernetes multi-tenancy presents security challenges due to shared resources among different services or teams, requiring isolation boundaries to ensure secure operations. The three primary isolation boundaries in Kubernetes include the Control Plane and API, where Kubernetes Namespaces and Role-Based Access Control (RBAC) help isolate tenants; the Host, leveraging containers and Linux features like Namespaces and cgroups for workload isolation; and the Network, where NetworkPolicies manage traffic between tenants. Tools like Falco and Open Policy Agent (OPA) Gatekeeper enhance security by monitoring runtime behaviors and enforcing policy compliance. Falco, an open-source project, alerts users to suspicious activities by analyzing Kubernetes audit trails and Linux syscalls, while OPA Gatekeeper acts as a firewall for Kubernetes configurations to prevent insecure deployments. Network isolation is achieved through NetworkPolicies, although challenges persist due to the need for external providers and the inherent default-allow nature of Kubernetes networking. Achieving effective multi-tenancy security involves configuring these boundaries, deploying monitoring tools, and tailoring them to specific organizational needs.