From: Stephen J. Smoogen (smooge@gmail.com)
Date: Sat Nov 12 2005 - 13:23:23 EST
On 11/11/05, John Hally <JHally@epnet.com> wrote:
> Hello All,
>
> I need a sanity check regarding DNS ACLs. For external facing DNS servers
> you need to allow only udp/53 inbound, correct? I know tcp/53 is used for
> zone transfers and requests/replies greater than a certain size, but they
> shouldn't typically happen for general dns queries correct?
>
I think that the backbone DNS servers and certain upstream DNS servers
require TCP, and if for some reason a query can not fit into a single
UDP packet it will switch to TCP.
So if you do not have insane hostnames or extra info (long TXT
sections etc), then TCP would not be needed to the world.. locking it
down so that it only talks to known upstream boxes would probably be
correct.
-- Stephen J Smoogen. CSIRT/Linux System Administrator ------------------------------------------------------------------------------ Audit your website security with Acunetix Web Vulnerability Scanner: Hackers are concentrating their efforts on attacking applications on your website. Up to 75% of cyber attacks are launched on shopping carts, forms, login pages, dynamic content etc. Firewalls, SSL and locked-down servers are futile against web application hacking. Check your website for vulnerabilities to SQL injection, Cross site scripting and other web attacks before hackers do! Download Trial at: http://www.securityfocus.com/sponsor/pen-test_050831 -------------------------------------------------------------------------------
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