Haha, a small explanation is in order. Your NAT type is determined by your connection. Assuming your looking at Modern Warfare 2 here. On a router, your NAT type will always show as Moderate, as you are using a wireless connection. If you had an ethernet cable plugged directly from your modem into your PS3, your NAT type would be high, as all internet resources would be dedicated directly to your PS3. I'm not 100% on how one would achieve a low NAT type though. These also go by types. Type 1 is high, Type 2 is moderate, Type 3 is low.
NAT is a firewall. It can be turned on and off. It affects how much info is abled to be forced into your system
Definitions of fire wall on the Web: •A combination of hardware and software that functions in a networked environment to prevent some forbidden communications / viruses. This is similar to the basic function of a firewall in building construction. ... by this definition it is a firewall. it prevents unwanted comunication from without the network.
WHAT DIFFERENCE DOES THAT MAKE? It is not a traditional firewall and is NEVER referred to as such. I told you the answer you were looking for, and even gave you a much better explanation on what you are obviously very unclear on.
Google "how to change my NAT type on my PS3" You should easily find some guides to push that into moderate.
http://www.pregamelobby.com/ps3-ps2-psone-discussions/5618-how-get-type-2-open-nat-your-ps3.html This is a nice extensive tutorial.
