This simple ruby script is used to generate a CIDR map usable for e.g. the Postfix MTA to except large email providers from things like blacklist checks.
It the amount of whitelist entries differ more than 10%, a warning is issued and the new file is not written. In that case, call the script again with "-f".
NOTE: This is by no means secure, a single changed line from e.g. 127.16.0.0./12 to e.g. 18.104.22.168/12 would no count towards the diff, but make a HUGE difference.
- read whitelist domains from file
- make change threshold configurable