Post-mortem on the Spamhaus DOS

There’s been a ton of press over the last week on the denial of service attack on Spamhaus. A lot of it has been overly excited and exaggerated, probably in an effort to generate clicks and ad revenue at the relevant websites. But we’re starting to see the security and network experts talk about the attack, it’s effects and what it tells us about future attacks.
I posted an analysis from the ISC yesterday. They had some useful information about the attack and about what everyone should be doing to stop from contributing to future attacks (close your open DNS resolver). The nice thing about this article is that it looked at the attack from the point of view of network health and security.
Today another article was published in TechWeekEurope that said many of the same things that the ISC article did about the size and impact of the attacks.
What’s the takeaway from this?

  • Yes, there was a very large attack (300Gbps).
  • The attack was focused at Spamhaus, and later some of the Internet Exchanges (IX).
  • The attack caused some sleepless nights for the folks handling the routers as they dealt with the traffic.
  • The attack caused some websites (some hosted by Cloudflare, some sharing network space with Cloudflare) to be offline for some period of time.
  • The attack wasn’t noticed by most end users.
  • The networks identified engineering issues that made this attack worse (open DNS resolvers, some engineering choices inside the IXs).
We’ll get back to email and delivery talk next week. I promise.

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Spamhaus under major dDOS

Late last night I, and a number of other folks, received mail from Spamhaus informing us of a major denial of service attack against their servers. The attack is so bad that the website and main mailserver is currently offline.
DNS services, including rsync and the mirrors, are up and running.
Spamhaus is working to bring the mailserver and website back up, and are hoping to have it up later today.
If there are any critical or particularly urgent SBL issues today, contact your ESP delivery team. The folks who were contacted do have an email address for urgent issues. This is not an address for routine queries, however, and most listees are going to have to wait until normal services are restored to have their listing addressed.
If there is something particularly urgent and your ESP or delivery team does not have a contact address, you can contact me an I can see what I can do.
UPDATE: Most of the IPs people have sent me are actually XBL/CBL listings. But right now the CBL webserver is responding slowly due to the DOS.
If you want to look up a listing without using the Spamhaus website you can use the “host” or “dig” command line tools. To do this reverse the digits in the IP address and append zen.spamhaus.org on the end.
So for the IP 10.11.12.13 you would query 13.12.11.10.zen.spamhaus.org

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CBL website and email back on line

The CBL website is back on line.
It’s possible that your local DNS resolver has old values for it cached. If so, and if you can’t flush your local DNS cache, and you really can’t wait until DNS has been updated then you may be able to put a temporary entry in your hosts file to point to cbl.abuseat.org.
You can get the IP address you need to add by querying the nameserver at ns-2038.awsdns-62.co.uk for cbl.abuseat.org. No, I’m not going to tell you the IP address – if you can’t do a basic DNS query, you shouldn’t be modifying your hosts file and you can just wait a day.

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