How do you test your router/firewall for security?

[Larry Cook]

Thanks for the responses.  I feel much better after having done some testing 
over the weekend.

The various test sites show that my Actiontec DSL modem/router responds that
the ports are closed, although a few ports don't respond at all.  These are
ports 135, 136, 137, 138, 139, 412, and 445, which I think are all ports used
by MS protocols.  At first I thought it was my router not responding, but I'm
wondering if they are being intercepted by my ISP.  I've emailed my ISP to 
find out.

Additionally, the router has the ability to specify an IP address as a DMZ
Host and forwards all connection requests to that host.  I did this for each 
of my hosts and found that my Win95 with ZoneAlarm didn't respond to any 
requests.  I was most nervous about my RH8 server running Samba, but amazingly 
that didn't respond to any requests either.  My RH8 desktop on the other hand 
responded that most ports were closed, but three were open to the internet. 
This was my first Linux system and I didn't know anything about iptables when 
I set it up.  I guess I'll have to go back and fix it.

This is a learning experience for me and I was pleased to see that iptables 
and ZoneAlarm can distingish between local and internet traffic.  This leads 
me to a few more questions:

What are the vulnerabilities that I should be concerned about that could let 
someone through my router and onto my local network?

If someone does get through to my local network, are all bets off, or will 
ZoneAlarm and iptables on each system provide additional security?

Thanks,
Larry