Along with the 'ipfw' firewall comes something called 'Adaptive Firewall'. OS X's "Network Services Administration" indicates that this adaptive firewall 'just works':
Adaptive FirewallApparently my Mac Air is doing something to annoy the Adaptive Firewall on my mini. After a day of running ipfw, my Air looses the ability to connect to the Mini Server and 'ipfw show' shows a deny any for the IP address of my Mac Air. I have no clue why it's blacklisting me - I'm connecting via AFP, Samba and Time Machine, all of which work fine until they don't.
Mac OS X v10.6 uses an adaptive firewall that dynamically generates a firewall rule if a user has 10 consecutive failed login attempts. The generated rule blocks the user’s computer for 15 minutes, preventing the user from attempting to log in.
The adaptive firewall helps to prevent your computer from being attacked by unauthorized users. The adaptive firewall does not require configuration and is active when you turn on your firewall.
Fortunately I keep a handful of Windows 7 laptops around. They don't get blacklisted even when I try.
To tweak the adaptive firewall start with:
sudo cat /etc/af.plist
sudo cat /var/db/af/blacklist
And when you get tired of being blacklisted by your own server:
/usr/libexec/afctl -w 192.168.0.0/24
The adaptive firewall may (or may not) log to:
depending on various sysctl, socketfilterfw and serveradmin settings. As far as I can tell, mine doesn't log anything. Interesting things like 'I've blacklisted you" apparently are worthy only of /dev/null.
I bought the Mini Server for my home network because after a decade of running Solaris, I've decided that I want simple, straight forward technology at home so I can spend less time reading man pages and tweaking config files.