Packet routing and local network security: TCP/IP vs. NetBEUI

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From: Paul (Paul_at_please.post.replies)
Date: 03/14/04 

Date: Sun, 14 Mar 2004 17:32:06 GMT

I've heard NetBEUI described as an "unroutable" network protocol where
supposedly machines on a local network using NetBEUI cannot talk to
the Internet by any means, but machines using TCP/IP can.

Suppose I have a local network of 4 machines. I want all 4 to be able
to talk to each other, but I only want 2 of them to talk to the
Internet. The reason to keep 2 machines from talking to the Internet
is I'm hoping this will prevent anyone from breaking into those 2
regardless what new Windows security bugs may be found.

The local network of 4 machines goes through a network switch to the
router which goes to the cable modem to the Internet. I always un-bind
TCP/IP from File and Printer Sharing under Windows 2000 and only use
NetBEUI for that service, but I leave both TCP/IP and NetBEUI bound to
the NIC adapter. If I un-bind TCP/IP from the NIC of the 2 machines I
want isolated, they can no longer talk to the Internet but they can
talk to the other 3 machines on the local network. On the surface this
appears to do what I want, but I'm wonder how secure it really is.

Question #1: Are my 2 machines with only NetBEUI bound to the NIC 100%
secure from any outside attacks since NetBEUI is unroutable and data
to/from these 2 machines cannot go outside my local network?

I know that routers are supposed to provide some firewall protection,
but that assumes the firmware does not have backdoors in it.

Question 2: Is the average router (mine is a Linksys BEFSR11) capable
of intercepting NetBEUI packets and translating them into TCP/IP to go
over the network or do routers by definition only handle TCP/IP?

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