Firewalls: DNS Client Ports

Firewalls
(March 1993)

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Subject:	DNS Client Ports
From:	Dave Mischler <mischler @ cubic . com>
Date:	Sat, 13 Mar 93 20:34:27 EST
To:	FireWalls @ GreatCircle . COM

I have recently added selective packet logging to my packet filter
code for KA9Q (it will be ready for release soon), and I have noticed
some DNS requests from non-privileged ports from various machines on
the net.  I am currently only allowing UDP DNS from any address with a
source port of 53 to reach my externally accessible name server.
Should I allow "random" client ports through?  What are the security
implications?

Dave Mischler
mischler @
 cubic .
 com

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