Copied from http://cr.yp.to/djbdns/forgery.html
February 2009 comments
I introduced UDP port randomization in the first dnscache release in December 1999. PowerDNS copied the same feature in 2006. As far as I know, between December 1999 and July 2008, all other DNS software on the Internet allowed blind attacks that were likely to succeed using fewer than 100000 packets.
Many DNS software authors issued "emergency" UDP-port-randomization patches in July 2008. Some of these patches, and some subsequent patches, also attempted to stop colliding attacks, by combining "duplicate-query suppression" with various other mechanisms. Kevin Day issued a patch of this type for dnscache in February 2009.
Day also issued a security alert ("CVE-2008-4392") stating that dnscache, without duplicate-query suppression, allowed a colliding attack using tens of millions of packets. Day failed to mention that exactly the same information has been available on this web page since November 2002. As far as I know, my July 2001 posting on the topic was the first publication of colliding attacks on DNS.
(more at link)