Minimize unknown keyword, Prevent the spammers

Is there any way to reduce the server to send fail return for any unknown keyword ?
We never know where is the spammer or mistaken keyword typed by the sender.

Maybe it will be better, If the unknown keyword come from the same number, the server should add that number into the blocked sender number.
So the next time, the server only log incoming sms from that numbers, but the server did not any response for that (forbidden) numbers.

Just leave an empty response for NOKEYWORD.

It will not be advisable to block all number that sends unknown keywords as legitimate users might send a typo. One possible way is to use the Mobile Security function - pls refer to VisualGSM Enterprise User Guide for details.