The simplest way to deal with this (IP address from specific hosts) is to use mod_rewrite to either block the "offending" IP address(es) or simply to allow the ones you wish to have access (and FAIL) all others. Actually, Allow/Deny statements would be better suited (as they are part of Apache's core directives).
allow from 192.168.0. # all in the LAN block
deny from all
At least you now have a place to start.