I did have a look for setup details for your router, but couldn't really find anything that helps. but I would have thought that simply ensuring the firewall is turned on in the router would be enough. incoming port 443 is certainly not something I'd expect most routers to leave open by default.
A thought did occur to me though, some ISPs redirect the common server ports to their own servers to stop people running web or mail servers on their home ADSL connection, if yours is one that does redirect then it may not be your computer that is open and it may just be that port is being redirected to another computer.