BGP hijack
termnetworkingsecurity
Announcing address space you do not hold, so that other networks send you traffic meant for its real owner - effective because routing prefers the most specific announcement and the protocol has no native way to check who is entitled to originate a prefix.
Impact is global within minutes and depends entirely on whether the upstream provider filtered. The dangerous variant is not blackholing but interception: divert, inspect, and forward on, so the destination keeps working and the only evidence is latency and a path nobody looks at. Route origin validation with RPKI closes the crude version; it does not close a plausible forged path, which is why monitoring your own prefixes remains an operational duty rather than an optional nicety.
Also known as: prefix hijack, route hijack, more specific announcement