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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Soulbender
Member since:
2005-08-18

but personally I'd rather see ISPs, peers and exchanges to add some reverse engineering to their UDP forwarding - in that they only forward UDP packets if the IP address attached can be routed backwards


This is already done by any competent provider and it is why spoofing is much less common today than it used to be. It's not feasible to do this between "Tier 1" peers though (due to, among other things, asymmetric routing) so it's important that providers closer to the customer does this properly.
This wouldn't solve the problem with DNS amplification attacks though since the source was valid and not spoofed. The only way to effectively stop these attacks is to not have open DNS resolvers.

Reply Parent Score: 2

Laurence Member since:
2007-03-26

The source was spoofed. That's how the amplification attack works:

1. send spoofed UDP packet to DNS server.
2. server then replies to the spoofed UDP packet.
3. and the target server goes down because the spoofed UDP packet has the target as the source IP.

It's a bit like me pinging Google pretending to be your IP. Then google responds be sending a reply to you instead of me. Except we're talking several orders of magnitude more bits being exchanged than in a simple IMCP echo request. And the DNS server replying with more data than they received as part of the domain name lookup request.

Reply Parent Score: 2