Firewall Wizards mailing list archives
Re: Does blocking TCP DNS packets keep your Bind safe?
From: Bill_Royds () pch gc ca
Date: Fri, 9 Mar 2001 10:25:22 -0500
Don Kendrick said: 2. Most if not all "normal" queries needed by legit Internet traffic are UDP. This is not at all true. Nowadays, requests for DNS over TCP for large reverse DNS lookups are very common. If you have a firewall that is verifying DNS for logs etc. you will have a large number of TCP DNS lookups for multi hosted web farms etc. You can still block it, but you may miss a lot of useful information in a security context. Don Kendrick <don () netspys com> on 03/07/2001 04:09:01 PM To: firewall-wizards () nfr net cc: (bcc: Bill Royds/HullOttawa/PCH/CA) Subject: [fw-wiz] Does blocking TCP DNS packets keep your Bind safe? OK, here I go again breaking things :) Over the years I've argued about blocking icmp at the border routers. Steve Bellovin et al would usually argue that it breaks path MTU, etc. I'd usually argue that we can rely on path MTU being negotiated elsewhere in the path (LAN vs. WAN bandwidth)...but I digress Here's what I am suggesting: 1. We should all only do zone transfers (TCP) with known secondaries. 2. Most if not all "normal" queries needed by legit Internet traffic are UDP. Why not just block port 53 TCP connections at the border routers except for our secondaries. Is it possible to do a buffer overflow or other DNS/Bind exploit via UDP? I don't know the answer, I'm asking. Don Don Kendrick, CNE, CCNA, GCIA, CISSP _______________________________________________ firewall-wizards mailing list firewall-wizards () nfr com http://www.nfr.com/mailman/listinfo/firewall-wizards
Current thread:
- Does blocking TCP DNS packets keep your Bind safe? Don Kendrick (Mar 09)
- Re: Does blocking TCP DNS packets keep your Bind safe? Gary Flynn (Mar 10)
- Re: Does blocking TCP DNS packets keep your Bind safe? M. Dodge Mumford (Mar 10)
- Re: Does blocking TCP DNS packets keep your Bind safe? David Lang (Mar 10)
- <Possible follow-ups>
- Does blocking TCP DNS packets keep your Bind safe? Don Kendrick (Mar 09)
- Re: Does blocking TCP DNS packets keep your Bind safe? John Adams (Mar 10)
- Re: Does blocking TCP DNS packets keep your Bind safe? Crist Clark (Mar 10)
- Re: Does blocking TCP DNS packets keep your Bind safe? Jeff Sedayao (Mar 10)
- Re: Does blocking TCP DNS packets keep your Bind safe? Andrew Huffer (Mar 10)
- Re: Does blocking TCP DNS packets keep your Bind safe? Bill_Royds (Mar 10)
- RE: Does blocking TCP DNS packets keep your Bind safe? Ben Nagy (Mar 11)
- Re: Does blocking TCP DNS packets keep your Bind safe? Luca Berra (Mar 13)
- RE: Does blocking TCP DNS packets keep your Bind safe? Todd (Mar 13)
- Re: Does blocking TCP DNS packets keep your Bind safe? Darren Reed (Mar 14)
- Re: Does blocking TCP DNS packets keep your Bind safe? Todd (Mar 14)
- Re: Does blocking TCP DNS packets keep your Bind safe? Darren Reed (Mar 14)