First, I used PureFTPd Manager for OSX (Linux or BSD OK). I need to have a block list file/firewall in /usr/ftpblock/ which is a list of usernames including with wildcards ( *wild* ). The list will have list of blocked usernames, one line per username. If remote user tries to FTP using username in the list, user is will see "You have been blocked". Then, at that time, the user's IP will also be automatically be added to the IP blocked list file. If file does not exist, create the file also in same dir /usr/ftpblock/. So next time user logged in from the same IP, user is blocked already and will display "You have been blocked".
Caution, firewall must not interfere with server comm. Only remote user in the list be blocked from coming in FTP or http.
Do not bid if you do not understand. Just do something else.
This project funding is only $[url removed, login to view] maximum. This is a very simple application.