] other cctld servers have seen what are effectively ddos. rob thomas ] seems to have the most clue on this, so i hope this troll will entice ] him to speak.
Did someone say "troll?" :)
Yes, this is a real problem. These attacks have exceeded several gigabits per second in size, and during one attack 122K DNS name servers were abused as amplifiers. Ouch!
This abuse can be mitigated. Here are a few tips.
<there has -GOT- to be a better name for this>
Limit recursion to trusted netblocks and customers. Do not permit your name servers to provide recursion for the world. If you do, you will contribute to one of these attacks.
<recursion is a fundamental DNS design feature, restricting it to "walled gardens" cripples its usefullness>
Watch for queries to your name servers that ask for "ANY" related to a DNS RR outside of the zones for which you are authoritative. This DNS RR will be LARGE.
<a valid concern, w/ the following caveat: LARGE, relative to current traffic>
Limit UDP queries to 512 bytes. This greatly decreases the amplification affect, though it doesn't stop it.
<limiting UDP to 512 has other, unwanted effects, edns0 for one... crippling ENUM, DNSSEC, IPv6, etc... is this really what is wanted?>
Scan your IP space for name servers that permit recursive queries. It's amazing just how many of these name servers exist.
<yup... again, a feature that has made the DNS as useful as it has become>
Refer to the following guides for some excellent insight and suggestions.
<http://www.us-cert.gov/reading_room/DNS-recursion121605.pdf> <http://cc.uoregon.edu/cnews/winter2006/recursive.htm> <http://dns.measurement-factory.com/surveys/sum1.html>
Note we have our own Secure BIND Template which will help on the BIND side of life.
<http://www.cymru.com/Documents/secure-bind-template.html>
If you need assistance with any of this, have endured one of these attacks, or have any other questions, please don't hesitate to ping on us at team-cymru@cymru.com. We're here to assist!
Thanks! Rob. -- Rob Thomas Team Cymru http://www.cymru.com/ ASSERT(coffee != empty);
ok, so i'm being a bit of a curmudgion here but just how, if we throttle DNS to the minimum suite for todays services, can we be expected to add new features/services? grump grump grump... -- (grumpy) bill