Many routers have port 0 open as a way of doing NAT. Any attempt to open port 0 from the WAN will result in the packet being redirected to an available port greater than 1025. There's no intrusion issue on having port 0 open, but there is one involving "fingerprinting" or identifying the router from the WAN side using the way port 0 is handled.
Let me explain,
I have a Netgear WGT624 wireless router, I have 3 PC's and all connect to the internet with WPA-PSK (TKIP) and a full 63 character key. I have firewalls on all the Computers and all ports are blocked except the ones needed for web,email access. My router has NAT/SPI and does not respond to pings etc.
Now all that say when I go to GRC's shields up and do an all ports scan it reports as failed and tells me port 0 is showing.
Have I been compromised or have I forgot to enable/disable something in the Router.
Thanks
JM
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