I am not sure how you can do this but this is what I am after:
Multiple words rejection in rules
It is known that it will take multiple keywords to co-ordinate an attack.
Just and only having SELECT in a query string is unlikely to do too much if no other keys are present. (Edit: thinking about it SELECT might be a example just SELECT might do some harm)
Now I want to reject a request if x keyterms are found.
Now by default I want this as 1 but I would like the option words in a given list to be rejected.
I might then have multiple rules. Say one specifically for CAST with count =1
And other more general ones can have count =2
This might stop 'false positives' with only 1 term appearing randomly. Obviously careful consideration is needed.
I hope you understand from that poor description.......I know this feature will be a long shot.