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Situation: I am currently seeing a huge wave of incoming DNS requests arriving in burst of around 85 queries per 2-3 seconds from one IP. Then another IP sends a new wave and so on (currently my DNS service is turned off, so that it does not take part in what looks like another amplification attack).

Question: Is there a way to set a query limit per IP?

It is very unlikely that the same client needs to resolve more than 2 or 3 domains within a second, so that sounds like a reasonable step.

  • How are you certain this is unlikely? Perhaps they are running a script or application that performs dns lookups. – Greg Askew Jun 2 '13 at 15:09
  • 85 querries over 2-3 seconds doesn't sound that malicious. Is it querries for the same FQDN? – Mathias R. Jessen Jun 2 '13 at 16:21
  • Yes, all for the same FQDN: directedat.asia: type ANY, class IN – Philip Allgaier Jun 2 '13 at 16:43
  • When you say inbound, to you mean from the Internet, or internally? Just asking, as it's possible to tunnel data through DNS queries. – Simon Catlin Jun 2 '13 at 18:31
  • Yes, from external IPs. – Philip Allgaier Jun 2 '13 at 19:34
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No shipping version of Windows Server has any built-in functionality to do rate-limiting like you're looking for, either in the IP stack or in the DNS server. You're stuck putting a firewall that can rate-limit in front of the Windows machine if you want this type of functionality.

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Philip is is possible that you are running a public Recursive DNS server?

I see that you currently have disabled your DNS service but your IP is most likely still in the 'servers to abuse' list of criminals.

What you can do:

  • Check if your public IP is listed on: openresolverproject.org

  • Disable recursion on your DNS server completely or only listen on an internal interface. See http://technet.microsoft.com/en-us/library/cc755068.aspx

  • Have a look at Bind DNS server under Linux. Its free and allows you to configer from what subnets you want to allow recursion.

Blog post on directedat.asia domain: http://dnsamplificationattacks.blogspot.com/2013/05/domain-directedatasia.html

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