Linked by Thom Holwerda on Thu 28th Mar 2013 00:36 UTC, submitted by MOS6510
Internet & Networking "The New York Times this morning published a story about the Spamhaus DDoS attack and how CloudFlare helped mitigate it and keep the site online. The Times calls the attack the largest known DDoS attack ever on the Internet. We wrote about the attack last week. At the time, it was a large attack, sending 85Gbps of traffic. Since then, the attack got much worse. Here are some of the technical details of what we've seen."
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Depending on which article you read, cloudflare was talking about two types of DDOS attacks.

You are talking about recursive DNS resolvers, which can be done without spoofing. But to be fair, this particular attack WAS based on spoofing the source IP as the victim to get the large DNS responses (rather than the small requests) to eat up their bandwidth. It's how the bandwidth multiplication was achieved.

"The basic technique of a DNS reflection attack is to send a request for a large DNS zone file with the source IP address spoofed to be the intended victim to a large number of open DNS resolvers. The resolvers then respond to the request, sending the large DNS zone answer to the intended victim. The attackers' requests themselves are only a fraction of the size of the responses, meaning the attacker can effectively amplify their attack to many times the size of the bandwidth resources they themselves control."

A non-spoofing recursive DNS attack is possible too, but it's not clear that this could have achieved the amount of bandwidth multiplication they got by spoofing the victim's IP. Let me know if I'm overlooking something.

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