On Jan 20, 2009, at 6:31 PM, David W. Hankins wrote:
On Tue, Jan 20, 2009 at 12:54:32PM -0800, Wil Schultz wrote:
Anyone else noticing "." requests coming in to your DNS servers?
I was surprised to see 'amplification' in the subject line here, since on my nameservers my replies are of equal length to the queries. A little bit of asking around, and I see that it is an amplification attack, preying on old software.
Let me sum up;
If you're running 9.4 or later, you will reply to these packets with 45 octet RCODE:Refused replies. 1:1. 9.4 has an "allow-query-cache" directive that defaults to track allow-recursion, which you should have set appropriately.
After reading this thread, I decided it was prudent to test my authoritative nameservers & was surprised to discover I could retrieve cached records from my nameserver even though I have "recursion no;" in my options stanza in named.conf. Re-reading the ARM, I see that behavior is expected. But is there some reason not to set "allow- recursion { none; };" since I already have recursion disabled? Thanks, Dave Coulthart