North American Network Operators Group
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Re: DNS - connection limit (without any extra hardware)

  • From: Douglas Otis
  • Date: Fri Dec 08 19:24:20 2006 
On Dec 8, 2006, at 6:40 AM, Luke wrote:
Hi,
as a consequence of a virus diffused in my customer-base, I often receive big bursts of traffic on my DNS servers. Unluckly, a lot of clients start to bomb my DNSs at a certain hour, so I have a distributed tentative of denial of service. I can't blacklist them on my DNSs, because the infected clients are too much.

For this reason, I would like that a DNS could response maximum to 10 queries per second given by every single Ip address. Anybody knows a solution, just using iptables/netfilter/kernel tuning/BIND tuning, without using any hardware traffic shaper?
One effective strategy is to make 0wning your customer's system less profitable. Here is a good article by Suresh Ramasubramanian:

http://www.circleid.com/posts/ port_25_blocking_or_fix_smtp_and_leave_port_25_alone_for_the_sake_of_spa m/

Some have been successful with notification tools such as those offered by:

http://www.perftech.com/

Customers are directed to a free scrub that does not depend upon OS validation status, such as Housecall.

-Doug