Two security researchers have demonstrated a new technique to stealthily intercept internet traffic on a scale previously presumed to be unavailable to anyone outside of intelligence agencies like the National Security Agency.
The tactic exploits the internet routing protocol BGP (Border Gateway Protocol) to let an attacker surreptitiously monitor unencrypted internet traffic anywhere in the world, and even modify it before it reaches its destination.
The man-in-the-middle attack exploits BGP to fool routers into re-directing data to an eavesdropper's network.
Anyone with a BGP router (ISPs, large corporations or anyone with space at a carrier hotel) could intercept data headed to a target IP address or group of addresses. The attack intercepts only traffic headed to target addresses, not from them, and it can't always vacuum in traffic within a network -- say, from one AT&T customer to another.
The method conceivably could be used for corporate espionage, nation-state spying or even by intelligence agencies looking to mine internet data without needing the cooperation of ISPs.
slides from Defcon: https://www.defcon.org/images/defcon-16/dc16-presentations/defcon-16-pilosov-kapela.pdf