Generally while doing sql injection, some sql keywords are used like union, select, from etc...the administrator filters these keywords so as to block such requests but it still becomes possible for an attacker to bypass these kind of filters
Example: the attacker attacks like this, index.php?id=1 union all select 1,2,3--n site gives response 406 not acceptable so by using tricks like this index.php?id=1 /*!union*/ /*!all*/ *!select*/ 1,2,3-- the attacker bypasses the security there are many ways to bypass this , it depends on how strongly the administrator has created the filter.
I have found this vulnerability scanner cracked ! You can download it for free of course from HERE
HOW TO INSTALL. INSTRUCTIONS !
The only thing that you have to do is to replace the files activation and wvs in the acunetix path. After that run acunetix and put a serial ex. 2-2-2-2-2-2-2-2-2-2 and complete the form !