Cilium is an open-source technology that delivers network security to large-scale containerized environments at the packet and application levels, integrating easily with Kubernetes clusters. It uses the Linux kernel's Berkeley Packet Filter (BPF) to enforce security policies using container identities or abstractions like Kubernetes service or pod, providing low performance overhead. Cilium integrates with Datadog to help ensure network policies are properly deployed and enforced, enabling visualization and alerting on key metrics such as endpoint regeneration, packet flow, and policy import errors. The technology tracks endpoint health and lifecycle events, monitors endpoint regeneration duration, and detects issues with policy imports, providing a comprehensive solution for securing containers made easy.