Open Policy Agent Gatekeeper vs Tetragon

Open Policy Agent Gatekeeper is a free, open-source Kubernetes policy controller for Linux and self-hosted deployments. It runs as a validating and mutating webhook, enforcing CRD-based policies evaluated by Open Policy Agent. Validation constraints can deny requests, warn, run in dry-run mode or report violations without changing resources. Mutation policies can alter matching resources during admission before validation checks the final object. An audit function periodically evaluates existing cluster resources against constraints to identify pre-existing misconfigurations. The project includes an extensible policy library with parameterized examples, and provider connections to external data such as image registries and directory services. Named integrations or backed services include Azure Policy for Kubernetes, Google Kubernetes Engine Policy Controller, Rancher, AWS EKS Blueprints and Alibaba Cloud. Installation options include prebuilt, development or locally built images and Helm. Gatekeeper requires Kubernetes resources introduced in version 1.16 and cluster-admin permissions for installation. The gator CLI is documented as beta from version 3.11.

Tetragon is a Kubernetes-aware security observability and runtime enforcement tool for Linux, container, and Kubernetes workloads. It uses eBPF to monitor activity, filter events, and enforce policies in the kernel in real time. Process reports can include executed binaries, command-line arguments, user IDs, parent processes, and start times. Tetragon also monitors file access and changes, and can block unauthorized file operations at the kernel level. Kubernetes policies can filter activity by namespace, pod labels, and container fields, with support for containerd and CRI-O. Network visibility ties events to processes and workloads and tracks connections, socket lifecycle, and bytes sent or received. The tool also monitors credential changes, kernel module activity, and eBPF program loads and interactions. Findings are available as JSON logs or through gRPC. Installation options include Helm on Kubernetes, released Linux packages, and a container image. Tetragon is a Cilium sub-project and a CNCF project, and is available as an open-source project with no paid plans listed.