BGP route leak
also: route leak, BGP hijacking (related), prefix leak
An unintended advertisement of BGP routing information by an autonomous system to other networks, causing traffic to be misdirected through an incorrect path on the internet.
A BGP route leak occurs when an autonomous system (AS) accidentally or due to misconfiguration advertises IP prefixes it should not be announcing. This causes other networks to believe incorrect routing paths exist, potentially redirecting internet traffic through the leaking AS.
Common causes include:misconfigured BGP filters, where an ISP fails to restrict route advertisements to only authorized prefixes; default route leaks, where a default route (0.0.0.0/0) is propagated instead of specific prefixes; and human error during configuration changes. For example, a small ISP might accidentally advertise Google's entire IP space to its upstream provider, causing global traffic intended for Google to route through that ISP instead.
BGP route leaks can cause widespread internet disruptions, service outages, and security risks. Notable incidents include the 2008 YouTube outage (Pakistan Telecom leaking YouTube prefixes) and the 2014 Indosat incident. Mitigation includes implementing RPKI (Resource Public Key Infrastructure) and BGP filters to validate and restrict route advertisements.