a chinese threat group designated velvet ant was found to have breached an isolated critical-infrastructure network in 2016 and held full administrative visibility for roughly ten years undetected. the access pivoted from internet-facing systems into an air-gapped environment that has no external path, meaning the intruders lived inside a network designed to be unreachable. a decade of unnoticed persistence in a supposedly sealed system is an unusually long undetected dwell time.