Cilium is open-source software that secures connectivity between services on Linux container platforms. Built on eBPF, a Linux kernel technology, it acts as a CNI plugin that provides the networking layer for Kubernetes. It also includes load balancing, network policy, a service mesh and Hubble observability. Policies can change without modifying application code. Cilium is deployed in the organisation's own clusters.
Cilium is licensed under Apache 2.0 for its user-space components, with its eBPF programs under GPL-2.0 or BSD-2-Clause, and it has CNCF graduated project status. It is governed by a group of maintainers and committers, and the project page names no company as owner. Its institutional home is therefore the Cloud Native Computing Foundation, part of the Linux Foundation, which has a mailing address in San Francisco. Because the code runs in the organisation's own clusters, traffic and data location stay under its control, and European organisations can inspect and operate the software without depending on a US cloud service.