RE: Which ports to block?

["Barber, Chris Mr. ATEC/Contractor" <Chris.M.Barber () atec army mil>]

Basically you would have a set of rules that would look similar to this

Deny ICMP Any Any
Allow from any to SMTP Server on port 25
Allow from InternalDNS to ExternalDNS on port 53
Allow from from InsideANY to OutsideANY on port 80
Deny Any Any

This will do what you have stated below, but it may not do what you actually
want.  Firewalls can do many great things, including break your network if
you are not careful.  Make sure you do not close the door that lets you
manage the firewall.
Make sure that any inbound rules you put in place allow traffic only to a
particular host and not the whole network.

Chris.

-----Original Message-----
From: Ferino Mardo [mailto:RMardo () ALJOMAIHBEV com] 
Sent: Saturday, July 24, 2004 4:04 AM
To: security-basics () securityfocus com
Subject: Which ports to block?

In setting up a "deny all" rule from a firewall, is it safe to block ports 0
to 65535 or only up to 1023? My interest are only to allow port
53 udp, 25, and 80.

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