>The attack described just now, is that this vulnerability combined with
>the traditional "birthday" attack scenario allows another form of
>attack. The birthday attacks in general are still possible on any DNS
>server which doesn't randomize source ports, but may be more difficult
>to conduct than this new attack. (I'm not sure, I haven't run the
>numbers.)

Thank you for the clarification, Tim.
That is exactly what I wanted to say. :)

By the way, as regards recent Bind 9, birthday attack is much more
difficult to conduct because even if the attacker sends multiple
simultaneous recursive queries, Bind 9 aggregates these queries.

In addition, there is a patch written by Jinmei-san for Bind 9.4.0
(current release) to randomize source ports.

http://www.jinmei.org/bind-9.4.0-portpool.patch
http://member.wide.ad.jp/tr/wide-tr-dns-bind9-portpool-01.txt
(technical report from WIDE project in Japanese)

Makoto Shiotsuki

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