Update: Gizmodo is calling bullshit on these claims. They're likely correct that this attack was not a "threat" to the overall internet, but I also believe that Gizmodo is underplaying the potential problems from open resolvers.
We've known for a while that there are a number of people out there who really
, one of the more well known providers of a blacklist of spam IP addresses. For what it's worth, there are times when it feels like Spamhaus may go overboard in declaring an IP or range of IP addresses as spammers. And, to some extent, because of that, it seems like some who use the Spamhaus list rely on it a bit too strongly. That said, Spamhaus is doing important work in helping to stop the internet from being overrun with spam, and that's a good thing. But sometimes those who it pisses off aren't particularly nice people. Last week, Spamhaus added hosting company Cyberbunker to its spamlist
. Someone didn't like that very much, and thus began a very big DDoS attack
using open DNS recursors. Spamhaus went to Cloudflare, who was able to mitigate the worst of the attack.
But... that just lead to round two, in which whoever was behind the DDoS went much, much bigger
attacking a bunch of the providers who provide Cloudflare with its bandwidth. Basically, it was massive firepower directed at some key points on the internet. And it was a pretty big deal. Cloudflare's blog post stays away from getting too expressive about the whole thing, but just the fact that they note the attack came close to "breaking" the internet should get you to wake up.
Tier 1 networks don't buy bandwidth from anyone, so the majority of the weight of the attack ended up being carried by them. While we don't have direct visibility into the traffic loads they saw, we have been told by one major Tier 1 provider that they saw more than 300Gbps of attack traffic related to this attack. That would make this attack one of the largest ever reported.
The challenge with attacks at this scale is they risk overwhelming the systems that link together the Internet itself. The largest routers that you can buy have, at most, 100Gbps ports. It is possible to bond more than one of these ports together to create capacity that is greater than 100Gbps however, at some point, there are limits to how much these routers can handle. If that limit is exceeded then the network becomes congested and slows down.
Over the last few days, as these attacks have increased, we've seen congestion across several major Tier 1s, primarily in Europe where most of the attacks were concentrated, that would have affected hundreds of millions of people even as they surfed sites unrelated to Spamhaus or CloudFlare. If the Internet felt a bit more sluggish for you over the last few days in Europe, this may be part of the reason why.
The attackers say they're protesting Spamhaus acting as the internet's police:
Questioned about the attacks, Sven Olaf Kamphuis, an Internet activist who said he was a spokesman for the attackers, said in an online message that, "We are aware that this is one of the largest DDoS attacks the world had publicly seen." Mr. Kamphuis said Cyberbunker was retaliating against Spamhaus for "abusing their influence."
"Nobody ever deputized Spamhaus to determine what goes and does not go on the Internet," Mr. Kamphuis said. "They worked themselves into that position by pretending to fight spam."
Of course, all of this has exposed clearly a big vulnerability in the setup of the internet, and suggest that slowing down the internet on a large scale is entirely possible. But it's also made security folks that much more aware of how urgent it is to fix the a key vulnerability that made this possible: the fact that there are so many open DNS resolvers out there
, that can be used to launch massive DDoS attacks. Because of that, security folks are rushing around to see if they can convince people to close as many of the approximately 21.7 million open resolvers out there:
While lists of open recursors have been passed around on network security lists for the last few years, on Monday the full extent of the problem was, for the first time, made public. The Open Resolver Project made available the full list of the 21.7 million open resolvers online in an effort to shut them down.
We'd debated doing the same thing ourselves for some time but worried about the collateral damage of what would happen if such a list fell into the hands of the bad guys. The last five days have made clear that the bad guys have the list of open resolvers and they are getting increasingly brazen in the attacks they are willing to launch. We are in full support of the Open Resolver Project and believe it is incumbent on all network providers to work with their customers to close any open resolvers running on their networks.
Basically, over the last week or so, there's been a war going on, concerning parts of the core of the internet, and while it might not have impacted you yet (or, maybe it did), it's likely that the next round will be even bigger. In the meantime, the race is on to shut down open resolvers to try to keep the internet working, and hopefully to cut down on the power of such attacks.