[CLUE-Tech] proper setup of NAT

[Mike]

All,

The power supply on my firewall recently died so after replacing it I
discovered that my firewall floppy disk was unreadable. I'm using Coyote
Linux.  After remaking the firewall floppy, I had a little trouble
getting the ports open that I wanted (22 and 25). So to debug this I did
a port scan using the site at www.auditmypc.com. In addition to the open
ports it returned this ominous sounding message:

	Notice!, your natted (or real) IP address is 192.168.0.10.
	This information can be used to track your activities.   I
	should not be able to obtain this information if your security
	is properly configured!

Okay, so what do I need to change/add to my iptables so that my real IP
address is hidden? And for background info, I know very little about
iptables. I'm looking for an exact command ;). (I know I should learn
more about iptables but so much to learn in Linux so little
time...sigh...I thought I would be better off getting a ready-made
firewall.)


On another security note I've gotten a handful of these type of log
messages:

Jul 30 21:20:06 xxx sshd[12529]: Illegal user test from 211.184.226.193
Jul 30 21:20:18 xxx sshd[19500]: User guest not allowed because shell
/dev/null is not executable


So someone in China or Korea is trying to log into my machine that is
behind the firewall. I have no user test on this system. I do have a
guest account but as the log says the shell is /dev/null. What is the
purpose of the guest account? Can I safely delete the guest account? Is
there still a risk with user test even though I have no user test? In
short, what should I check or change to make sure these knuckleheads
don't get in? I've recently ran chkrootkit and all was okay from that
aspect. Anything else I should check to make sure this box hasn't been
cracked?

Thanks for the help,

Mike