From: William Herrin Sent: Friday, January 14, 2011 4:11 PM To: nanog@nanog.org Subject: Re: Is NAT can provide some kind of protection?
On Fri, Jan 14, 2011 at 2:43 PM, Owen DeLong <owen@delong.com> 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