Security gain from NAT

Howard C. Berkowitz hcb at
Mon Jun 4 19:28:17 UTC 2007

I'm sure everyone understands the underlying principle, but I'm constantly
making the point that even the best firewall is not a total security
solution. Forget antivirus, IDS, host authentication, etc., and just look on
the perimeter.

At least four device types lead inside from the DMZ:
   Firewalls of various flavors
   VPN concentrators/security gateways
   Rate-limiting anti-DOS devices to protect host-to-host encryption

For small and medium enterprises, these functions might, as an
implementation choice, reside in the same box; NAT is most likely to coexist
with firewalling or VPN concentration. The latter gets a little Zen-ish if
the VPN concentrator acts as a separately addressed proxy anyway.

-----Original Message-----
From: owner-nanog at [mailto:owner-nanog at] On Behalf Of Sam
Sent: Monday, June 04, 2007 3:04 PM
To: Joe Abley
Cc: Jim Shankland; Owen DeLong; NANOG list
Subject: Re: Security gain from NAT

Joe Abley wrote:
> On 4-Jun-2007, at 14:32, Jim Shankland wrote:
>> Shall I do the experiment again where I set up a Linux box
>> at an RFC1918 address, behind a NAT device, publish the root
>> password of the Linux box and its RFC1918 address, and invite
>> all comers to prove me wrong by showing evidence that they've
>> successfully logged into the Linux box?
> Perhaps you should run a corresponding experiment whereby you set up a 
> linux box with a globally-unique address, put it behind a firewall 
> which blocks all incoming traffic to that box, and issue a similar 
> invitation.
> Do you think the results will be different?
I fear a somewhat more cynical person could interpret the results of 
such an experiment to mean that NAT is as good as a firewall ;)


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