I'm sure it won't be much help, but if you are interested in looking into it yourself:
https://vborg.vbsupport.ru/showthrea...threadid=76270
That link does it (very sloppy, I might add) but instead of input questions, which would be much easier to implement, it checks IP bits.
The file you want to look into is
includes/functions_login.php which is where the conditions are checked for login. Just read through it and where it is checking for password matching, add in and && AND condition to check if the input matches a database field that you will add.
Again, if you're just looking for someone to come up with this hack, none of this will be much use to you~