BGP

The Border Gateway Protocol is used especially by anyone needing to manage multiple network connections (e.g. for Load Balancing, automatic fallover in case of ISP outage, etc.).

The BGP protocol has giant security holes, but would be expensive to fix. However, a misconfigured router, or one that has been compromised by an online intruder, can cause chaos by advertising itself as the best path to an unrelated network. That's because routers using BGP implicitly trust their neighbors on the Internet--they don't ask for any sort of digital identification.