irule needed depend on URL not site ip

If you just want to drop requests made by IP address, you could do a simple test for any alpha character instead of a specific white list. This would be less specific but more efficient than checking a datagroup for every request.

Here's an untested example:

when HTTP_REQUEST {

   if { not [string match {*[a-zA-Z]*} [HTTP::header host]] }{
      discard
   }
}

Aaron