A BGP hijack is a routing abuse where a network falsely advertises ownership of an IP prefix, or advertises a more attractive path, so internet traffic is sent to the wrong destination. Because BGP is the system that connects autonomous networks, other routers may accept the bad announcement and redirect flows without any obvious break-in at the target host.
This matters in cyber security because the detour can be used to steal data, disrupt services, or place malicious content in the path to a trusted service. In real attacks, hijacked routes may expose users to fake login pages, intercepted updates, or delayed traffic while defenders work to restore the correct route. Common defenses include route origin validation with RPKI, monitoring for unexpected AS-path changes, and verifying software updates cryptographically so trust does not depend only on the network path.