Rich: Was out of town for the past several days, so I haven't checked in til now. Yup, got me again.
Kudos on looking into it to this level and upgrading the hardware. I don't want to be a downer, but you might need to upgrade vbulletin as well, this old version has many published vulnerabilities (not that the newer versions are necessarily more secure, they just have
different holes).
Upgrading vbulletin can be quite the pain in the butt too, but if you plop your current install down on a new box the problem will still exist if it's within your install. It's extremely unlikely that it's a problem down as deep as linux or apache, most likely it's vbulletin that has been hacked.
If you look at the chain of events this is what I logged just now:
Referer:
http://www.cornsnakes.com/forums/showthread.php?t=133252&page=10
GET /forums/clientscript/vbulletin_global.js?v=373 HTTP/1.1
Host:
www.cornsnakes.com
HTTP/1.1
302 Found
Location:
http://j9v9jks7rg96aymzoce03gw.alum...yaXB0L3ZidWxsZXRpbl9nbG9iYWwuanMlM2Z2PTM3Mw==
This says, I went to the Referer url and requested /forums/clientscript/vbulletin_global.js?v=373 as my normal course of business. Somewhere in that script it told my browser to redirect (302 Found) to the Location url (which then did a couple of redirects for itself to keep track of who gets paid for sending us to the adult websites).
The Location url has the ?g= parameter passed in which if you do a base 64 decode really reads:
js=1&smcntnkw=oxqcvci&time=1310140214447349341&src=145&surl=www.cornsnakes.com&sport=80&key=9E7694A0&suri=/forums/clientscript/vbulletin_global.js%3fv=373
This one is also suspect to me:
http://www.cornsnakes.com/forums/clientscript/vbulletin_menu.js?v=373
They bothered recording the script that got you there (vbulletin_global.js (v373)), so I'm looking at that as a big red flag twice now. I would check if that has been changed recently or if you might be able to roll back to an older version perhaps). I don't know what you might have changed on that to get to version 373. In the vbulletin admin area it logs admin access, so you can check if someone has been in there mucking around (I've seen them weasel their way in and give themselves admin access). You know what day it started since you have an active site and the OP was right on it.
It could be that those scripts have been tampered with, or possibly that whatever they're designed to do naturally is happening and inserting some other malicious code or similar.
Good luck, I think you're hot on their trail.