incrediBILL - 7:07 pm on Dec 12, 2011 (gmt 0)

One thing I noticed is that this bot is requesting only one page on my site.

If you're on Linux and have SSH access, this quick command will generate a nice temporary IP block list in seconds that you can drop in .htaccess until they go away.

grep "/attacked_page.php" -i access_log | egrep -o "[0-9]+\.[0-9]+\.[0-9]+\.[0-9]" | sort | uniq | awk '{print "deny "$1}'

That'll spit out a nice deny list you can drop in .htacess and shut down the known bad IPs while you try to figure the problem out and get it sorted.