How to track DNS resolution sources
Hi! I hope I'm wording this correctly. I had a incident at a client site where a DNS record was being spoofed. How does one track down the IP address that's returning the false records ? What tool can one use? Thanks! -- Sent from MetroMail
On the command line: host spoofed.host.name.com On Dec 3, 2014, at 11:22 AM, Notify Me <notify.sina@gmail.com> wrote:
Hi!
I hope I'm wording this correctly. I had a incident at a client site where a DNS record was being spoofed. How does one track down the IP address that's returning the false records ? What tool can one use?
Thanks!
-- Sent from MetroMail
On Wed, Dec 03, 2014 at 11:32:08AM -0500, TR Shaw <tshaw@oitc.com> wrote a message of 20 lines which said:
On the command line:
host spoofed.host.name.com
Excuse me but it is useless. It tests only the local resolver (which may be unpoisoned). It provides no details that could help to debug the problem (such as the TTL).
On Wed, Dec 03, 2014 at 05:22:58PM +0100, Notify Me <notify.sina@gmail.com> wrote a message of 13 lines which said:
I hope I'm wording this correctly.
Not really :-)
I had a incident at a client site where a DNS record was being spoofed.
How do you know? What steps did you use to assert this? Answers to these questions would help to understand your problem.
How does one track down the IP address that's returning the false records ?
If it's real DNS spoofing (which I doubt), the source IP address of the poisoner is forged, so it would not help. The main tool to use is dig. Let's assume the name that bothers you is foobar.example.com. Query your local resolver: dig A foobar.example.com Query an external resolver, here Google Public DNS: dig @8.8.4.4 A foobar.example.com Query the authoritative name servers of example.com. First, to find them: dig NS example.com Second, query them (replace the server name by the real one): dig @a.iana-servers.net. A foobar.example.com
Date: Wed, 3 Dec 2014 17:56:23 +0100 From: bortzmeyer@nic.fr To: notify.sina@gmail.com Subject: Re: How to track DNS resolution sources CC: nanog@nanog.org
On Wed, Dec 03, 2014 at 05:22:58PM +0100, Notify Me <notify.sina@gmail.com> wrote a message of 13 lines which said:
I hope I'm wording this correctly.
Not really :-)
I had a incident at a client site where a DNS record was being spoofed.
How do you know? What steps did you use to assert this? Answers to these questions would help to understand your problem.
How does one track down the IP address that's returning the false records ?
If it's real DNS spoofing (which I doubt), the source IP address of the poisoner is forged, so it would not help.
The main tool to use is dig. Let's assume the name that bothers you is foobar.example.com. Query your local resolver:
dig A foobar.example.com
Query an external resolver, here Google Public DNS:
dig @8.8.4.4 A foobar.example.com
Query the authoritative name servers of example.com. First, to find them:
dig NS example.com
Second, query them (replace the server name by the real one):
dig @a.iana-servers.net. A foobar.example.com
I didn't understand how this will help him identify the poisoner. What an IDS rule will do is check for responding authoritative query IDs for DNS queries never made to that responder, but made for the authoritative server identified as per above (direct NS inquiry). If no IDS is present, BIND logging would allow for identification of authoritative responses and query ID identification. In summary whatever is answered authoritatively by a server other than the NS ones tracked by "dig +trace foobar.examplecom" is the potential poisoner. But if the poisoing is done from an spoofed IP address (spoofing the authoritative IP), well good luck w/ that if the spoofed domain is not DNSSEC aware.
participants (4)
-
Notify Me -
Stephane Bortzmeyer -
teleric team -
TR Shaw