QUOTE(bluedevils @ Mar 15 2005, 12:46 AM)
"netstat -a" while you are connected to a network should tell you what services are listening (open). You could also install iptables and setup a tight firewall.
So, basically, lock down networked ports to stop stuff coming in.
If you're not sure about putting passwords on accounts, then put your public ssh key into the authorized_keys files for each user, then change the sshd config to not allow plain text passwords, that way the lack of passwords doesn't matter... also, you can put specific users into the sshd config which are allowed to login, and thus prevent attempting to log in to the Zaurus account for example.
Don't forget to save a copy of the old config files first.