Huge chunks of Internet traffic belonging to financial institutions, government agencies, and network service providers have repeatedly been diverted to distant locations under unexplained circumstances that are stoking suspicions the traffic may be surreptitiously monitored or modified before being passed along to its final destination.

Researchers from network intelligence firm Renesys made that sobering assessment in a blog post published Tuesday. Since February, they have observed 38 distinct events in which large blocks of traffic have been improperly redirected to routers at Belarusian or Icelandic service providers. The hacks, which exploit implicit trust placed in the border gateway protocol used to exchange data between large service providers, affected "major financial institutions, governments, and network service providers" in the US, South Korea, Germany, the Czech Republic, Lithuania, Libya, and Iran.

Further Reading Insecure routing redirects YouTube to Pakistan

The ease of altering or deleting authorized BGP routes, or of creating new ones, has long been considered a potential Achilles Heel for the Internet. Indeed, in 2008, YouTube became unreachable for virtually all Internet users after a Pakistani ISP altered a route in a ham-fisted attempt to block the service in just that country. Later that year, researchers at the Defcon hacker conference showed how BGP routes could be manipulated to redirect huge swaths of Internet traffic . By diverting it to unauthorized routers under control of hackers, they were then free to monitor or tamper with any data that was unencrypted before sending it to its intended recipient with little sign of what had just taken place.

"This year, that potential has become reality," Renesys researcher Jim Cowie wrote. "We have actually observed live man-in-the-middle (MitM) hijacks on more than 60 days so far this year. About 1,500 individual IP blocks have been hijacked, in events lasting from minutes to days, by attackers working from various countries."

At least one unidentified voice-over-IP provider has also been targeted. In all, data destined for 150 cities have been intercepted. The attacks are serious because they affect the Internet equivalents of a US interstate that can carry data for hundreds of thousands or even millions of people. And unlike the typical BGP glitches that arise from time to time, the attacks observed by Renesys provide few outward signs to users that anything is amiss.

"The recipient, perhaps sitting at home in a pleasant Virginia suburb drinking his morning coffee, has no idea that someone in Minsk has the ability to watch him surf the Web," Cowie wrote. "Even if he ran his own traceroute to verify connectivity to the world, the paths he'd see would be the usual ones. The reverse path, carrying content back to him from all over the world, has been invisibly tampered with."

Guadalajara to Washington via Belarus

Renesys observed the first route hijacking in February when various routes across the globe were mysteriously funneled through Belarusian ISP GlobalOneBel before being delivered to their final destination. One trace, traveling from Guadalajara, Mexico, to Washington, DC, normally would have been handed from Mexican provider Alestra to US provider PCCW in Laredo, Texas, and from there to the DC metro area and then, finally, delivered to users through the Qwest/Centurylink service provider. According to Cowie:

Instead, however, PCCW gives it to Level3 (previously Global Crossing), who is advertising a false Belarus route, having heard it from Russia’s TransTelecom, who heard it from their customer, Belarus Telecom. Level3 carries the traffic to London, where it delivers it to Transtelecom, who takes it to Moscow and on to Belarus. Beltelecom has a chance to examine the traffic and then sends it back out on the “clean path” through Russian provider ReTN (recently acquired by Rostelecom). ReTN delivers it to Frankfurt and hands it to NTT, who takes it to New York. Finally, NTT hands it off to Qwest/Centurylink in Washington DC, and the traffic is delivered.

Such redirections occurred on an almost daily basis throughout February, with the set of affected networks changing every 24 hours or so. The diversions stopped in March. When they resumed in May, they used a different customer of Bel Telecom as the source. In all, Renesys researchers saw 21 redirections. Then, also during May, they saw something completely new: a hijack lasting only five minutes diverting traffic to Nyherji hf (also known as AS29689, short for autonomous system 29689), a small provider based in Iceland.

Renesys didn't see anything more until July 31 when redirections through Iceland began in earnest. When they first resumed, the source was provider Opin Kerfi (AS48685).

Cowie continued:

In fact, this was one of seventeen Icelandic events, spread over the period July 31 to August 19. And Opin Kerfi was not the only Icelandic company that appeared to announce international IP address space: in all, we saw traffic redirections from nine different Icelandic autonomous systems, all customers of (or belonging to) the national incumbent Síminn. Hijacks affected victims in several different countries during these events, following the same pattern: false routes sent to Síminn's peers in London, leaving 'clean paths' to North America to carry the redirected traffic back to its intended destination.

In all, Renesys observed 17 redirections to Iceland. To appreciate how circuitous some of the routes were, consider the case of traffic passing between two locations in Denver. As the graphic below traces, it traveled all the way to Iceland through a series of hops before finally reaching its intended destination.

Cowie said Renesys' researchers still don't know who is carrying out the attacks, what their motivation is, or exactly how they're pulling them off. Members of Icelandic telecommunications company Síminn, which provides Internet backbone services in that country, told Renesys the redirections to Iceland were the result of a software bug and that the problem had gone away once it was patched. They told the researchers they didn't believe the diversions had a malicious origin.

Cowie said that explanation is "unlikely." He went on to say that even if it does prove correct, it's nonetheless highly troubling.

"If this is a bug, it's a dangerous one, capable of simulating an extremely subtle traffic redirection/interception attack that plays out in multiple episodes, with varying targets, over a period of weeks," he wrote. "If it's a bug that can be exploited remotely, it needs to be discussed more widely within the global networking community and eradicated."