you should capcha set in user registion or rewrite in .htaccess <Files ".htaccess"> Mã: deny from all </Files> order allow,deny allow from all deny from 58.14.0.0/15 <- your IP block deny from 58.16.0.0/13 deny from 58.24.0.0/15 deny from 58.30.0.0/15 deny from 58.32.0.0/11
My choice is qaptcha (http://vietxf.org/threads/xf-qaptcha-1-1.4257/) , it's smart way to fighting with spam bot