Is there a reliable way to counter people who ip spoof in mybb forum? IP banning seems to be an unreliable option as they can keep changing their ip.
You could create a .htaccess file in the root of your forum, and put in
deny from xxx.xxx.xxx.*
Where the x's are the respective sections of the ip address.
Thats if the ips they keep changing to are all from the same subnet e.g. 123.456.789.1 , 123.456.789.2 , 123.456.789.3 etc.