Is NAT can provide some kind of protection?

Leen Besselink leen at
Sat Jan 15 06:24:01 CST 2011

On 01/15/2011 02:01 AM, George Bonser wrote:
>> From: William Herrin 
>> Sent: Friday, January 14, 2011 4:11 PM
>> To: nanog at
>> Subject: Re: Is NAT can provide some kind of protection?
>> On Fri, Jan 14, 2011 at 2:43 PM, Owen DeLong <owen at> wrote:
>>> Ah, but, the point here is that NAT actually serves as an enabling
>>> technology for part of the attack he is describing.
>> I watch the movies too and I hang in suspense as the protagonist waits
>> for the bad guy to make a network connection and then activates the
>> phlebotinum that backhacks his tubes. And I know there are some
>> real-life examples where giving a hacker a large file to download has
>> kept him connected to a modem long enough to get a phone trace. But I
>> haven't read of a _nonfiction_ example where the dynamic opening in a
>> stateful firewall (NAT or otherwise) has directly provided the needed
>> opening for an _active_ attack by a third party. Can you cite one?
> The extent to which NAT is a security hazard in my experience is that it
> simply makes it harder to find a compromised machine.  Someone might
> inform us that they are seeing suspicious traffic that matches a virus
> profile from an IP address but the NAT makes it difficult to determine
> the actual source of the traffic.  In that case NAT isn't, in and of
> itself, the enabling mechanism, but it does offer the compromised host
> some additional time to do its malicious work while it is being tracked
> down and eliminated.
> It also adds more work for providers when someone wants to know who was
> responsible for certain traffic at certain times.  This is particularly
> true of NAT devices that get their "outside" IP by DHCP.  Now they have
> to search their records and sort out who had that IP at that time and
> then associate that with a specific customer.  Then at the customer
> location, there might be several more devices (or a neighbor connected
> over an unsecured wireless) and at that point there is no telling where
> the traffic came from.
> So NAT itself isn't a security threat, but it sure gives a real security
> threat a lot of woodwork in which to hide.
> G

I'm a full supported for getting rid of NAT when deploying IPv6, but
have to say the alternative is not all that great either.

Because what do people want, they want privacy, so they use the
IPv6 privacy extensions. Which are enabled by default on Windows
when IPv6 is used on XP, Vista and 7.

And now you have no idea who had that IPv6-address at some point
in time. The solution to that problem is ? I guess the only solution is to
have the IPv6 equivalant of arpwatch to log the MAC-addresses/IPv6-
address combinations ?

Or is their an other solution I'm missing.

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