Security Basics mailing list archives

Re: DNS Records


From: "Anders Reed Mohn" <anders_rm () utepils com>
Date: Thu, 19 Jun 2003 14:10:09 +0200



Yes it is possible if you allow any host(ip address) to do zone
transfers. Most name server daemons allow you to specify what hosts you
want to allow to request transfers, and block all others. You can also
block TCP port 53, and only allowing UDP port 53 with an ACL or Firewall
ruleset. I do both.


Careful..  blocking TCP 53 might break certain Microsoft-sw DNS lookups.
Apparently, Exchange, IIS and other MS software has a tendency of using TCP
53
for their DNS queries. (Requests too large for a UDP packet)

You're also breaking the RFC (1035), which specifies that both TCP and UDP
should be left open.

Cheers,
Anders :)


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