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DNS DoS ???

I've seen this for the same on about 3 sets of nameservers I operate.  fail2ban doing a 72 hour iptables drop rule.

-----Original Message-----
From: Drew Weaver [mailto:drew.weaver at thenap.com] 
Sent: Friday, July 29, 2011 3:01 PM
To: 'Elliot Finley'; nanog at nanog.org
Subject: RE: DNS DoS ???

We've been seeing this for several years on and off.


-----Original Message-----
From: Elliot Finley [mailto:efinley.lists at gmail.com]
Sent: Friday, July 29, 2011 2:51 PM
To: nanog at nanog.org
Subject: DNS DoS ???

my DNS servers were getting slow so I blocked recursive queries for all but my own network.

Then I was getting so many of these:

ns2 named[5056]: client query (cache) 'isc.org/ANY/IN' denied

that is was still slowing things down.  I've since written a script to watch the log and throw these into the box local firewall.  If I expire the entries after 24 hours then I accumulate about 10200 unique IPs.  If I expire after 48 hours, then it's just over 20000 unique IPs.

Is anyone else seeing this?