...
Scans with a Router
If your Internet connection uses a router (an option for xDSL, cable and satellite connections - not dial-up however) then that router will have its own Internet address and will use Network Address Translation (NAT) to amend packets allowing you to share the Internet connection between several computers. This is an advantage security-wise since the router will be visible on the Internet rather than your computer, but it can make certain applications and online scans harder to set up.
In this case, check the router's configuration - many can be set to give "stealthed" ports but the exact details will depend on the make and model of router. If you do not have appropriate documentation on this, then try an Internet search to see what other users have done.
To scan your PC (and Outpost) you will need to either:
- Reconfigure your router (temporarily!) to pass all incoming packets to your computer - this may be refered to as creating a DMZ, DeMilitarized Zone, or Port Forwarding (for all ports) or;
- Disconnect from your router and use a dial-up connection for the duration of the test only.
Scans with Proxy Servers
If you do not use a router but still have different IP addresses reported, then the next most likely cause is a proxy server. These are common in work or school environments and may be used by some ISPs. In such a case, there may no easy method of obtaining a direct connection, other than attempting a dial-up connection (with another ISP if possible). If in doubt, contact the proxy administrator.
ISP Filtering
There have been cases of people getting "Closed" results for certain ports without having a router or proxy server. In such cases, it is possible that the ISP is blocking some ports and returning an error message in order to prevent the spread of certain worms or trojans. This is most likely for ports widely used by such worms - notably 135-139 and 445.
