I'm not sure if this is against the rules of the site. If it is, please let me know and I'll delete the question.
I've seen variations of this script floating around recently. What the heck is it, and what does it do? http://pastebin.com/1XcMTsiL
You can see a list of sites that have been hit with it here: (For the love of god, DON'T click these links unless sandboxed).
There is a discussion here as well: http://www.webhostingtalk.com/showthread.php?t=1033395