RE: Which ports to block?

From: Barber, Chris Mr. ATEC/Contractor (Chris.M.Barber_at_atec.army.mil)
Date: 07/26/04

  • Next message: Depp, Dennis M.: "RE: fax software in the domain" 
    To: security-basics@securityfocus.com
Date: Mon, 26 Jul 2004 15:05:40 -0400

    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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  • Next message: Depp, Dennis M.: "RE: fax software in the domain"

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