FYI I have done this CIDR blocking for years at the firewall level ( people on the list harassed me about it) with minimal false positives but still enough to be a pain.
I have lists from Turkey, Russia and other countries as well, but using the firewall method was rough when people didn't get a rejection so what I did is I converted to postfix CIDR and use fail2ban to monitor the log. If I bounce the same IP 4 times with CIDR block then I block it at the firewall level saving the potential backscatter and making my postfix from overworking. I can tell you I have blocked MILLIONS of messages regularly from these CIDR's and it does make a big difference in the spam level. Good Luck Jack
