Hello,
I've decided to create one more release in the 1.2x stable branch to add source port randomization (for both NAT and the DNS forwarder). This is a recommended upgrade for all 1.2x users, no matter whether you're running a DNS server behind m0n0wall with NAT or not.
Download it at:
http://m0n0.ch/wall/downloads.php1.3b14 (which will also include NAT source port randomization; 1.3b13 so far only contains source port randomization for the built-in DNS forwarder) will be released soon.
Regards,
Manuel