How do you block anonymous surfer using htaccess?

Please help me, I have a surfer coming to my forum (phpBB) and posting using some anonymizer software that is giving fake IP's on every post he makes and making insult post...
I can't be blocking fake' IP's all day long and ban the user and have them keep coming back every other day ...
is there a way I can block the anonimous/anonimizer software access to my site using htaccess?

Please help me.
Thank You.

 

 

 

 

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