The Cyberweapon That Could Take Down the InternetS





Surgical strike



An attacker deploying the Schuchard cyberweapon would send traffic between computers in their botnet to build a map of the paths between them. Then they would identify a link common to many different paths and launch a ZMW attack to bring it down. Neighbouring routers would respond by sending out BGP updates to reroute traffic elsewhere. A short time later, the two sundered routers would reconnect and send out their own BGP updates, upon which attack traffic would start flowing in again, causing them to disconnect once more. This cycle would repeat, with the single breaking and reforming link sending out waves of BGP updates to every router on the internet. Eventually each router in the world would be receiving more updates than it could handle – after 20 minutes of attacking, a queue requiring 100 minutes of processing would have built up.

Clearly, that's a problem. "Routers under extreme computational load tend to do funny things," says Schuchard. With every router in the world preoccupied, natural routing outages wouldn't be fixed, and eventually the internet would be so full of holes that communication would become impossible. Shuchard thinks it would take days to recover.

"Once this attack got launched, it wouldn't be solved by technical means, but by network operators actually talking to each other," he says. Each autonomous system would have to be taken down and rebooted to clear the BGP backlog.

Meltdown not expected



Sitting duck

Whoever launched the attack, there's little we could do about it. Schuchard's simulation shows that existing fail-safes built into BGP do little to protect against his attack – they weren't designed to. One solution is to send BGP updates via a separate network from other data, but this is impractical as it would essentially involve building a shadow internet.

Another is to alter the BGP system to assume that links never go down, but this change would have to be made by at least 10 per cent of all autonomous systems on the internet, according to the researchers' model, and would require network operators to monitor the health of connections in other ways. Schuchard says that convincing enough independent operators to make the change could be difficult.

"Nobody knows if it's possible to bring down the global internet routing system," says Mark Handley, an expert in networked systems at University College London. He suggests that the attack could cause "significant disruption" to the internet, with an effect greater than the Slammer worm of 2003, but it is unlikely to bring the whole thing down.

"The simulations in the paper make a lot of simplifying assumptions, which is necessary to simulate on this scale," he explains. "I doubt the internet would behave as described."

Schuchard and colleagues presented their findings at the Network and Distributed System Security Symposium in San Diego, California, on Tuesday.

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