Figure 1. Default configuration of Mac OS X firewall with everything disabled

root# ipfw list
02000 allow ip from any to any via lo*
02010 deny ip from 127.0.0.0/8 to any in
02020 deny ip from any to 127.0.0.0/8 in
02030 deny ip from 224.0.0.0/3 to any in
02040 deny tcp from any to 224.0.0.0/3 in
02050 allow tcp from any to any out
02060 allow tcp from any to any established
02065 allow tcp from any to any frag
12190 deny log tcp from any to any
20000 deny log icmp from any to me in icmptypes 8
20310 allow udp from any to any dst-port 53 in
20320 allow udp from any to any dst-port 68 in
20321 allow udp from any 67 to me in
20322 allow udp from any 5353 to me in
20340 allow udp from any to any dst-port 137 in
20350 allow udp from any to any dst-port 427 in
20360 allow udp from any to any dst-port 631 in
20370 allow udp from any to any dst-port 5353 in
30510 allow udp from me to any out keep-state
30520 allow udp from any to any in frag
35000 deny log udp from any to any in
65535 allow ip from any to any