What the....!!!

[shohin]

A few days ago I had a small issue, but it was resolved. I'm admittedly technically deficient so I had someone (very reliable) update my site to 3.8.6 PL 1 as long as he was working on it, and suggested by him. All was well for about a week, but suddenly I just got slammed with something I've NEVER run across before!

I've received several emails from some members of my site (those few who happened to have it) and notified me that they cannot get on the site and get a Warning from their Anti-Virus program. Makes no difference what Anti-Virus program it is, i.e. Norton or, as in my case, AVG. I've included the two images of what I get when I try to access my site. Just what is this, and what on earth can I do??? HELP!!

[Alfa1]

Start by changing the ftp password and lock out the person that has upgraded your site.
Then have everyone with ftp access scan their PC with 2 different antivirus applications.
When all is clean and you are sure that none of the computers contains a virus, then you need to find the pages on your site that have malicious code in there.
Is stopbadware.org already reviewing your website or is google search showing alerts for it? If so then this will give you an overview of the pages that have malicious code. Reupload vbulletin, but make sure to check the files before you do. Its possible they are modified by a virus/worm. Its best to download it from vb.com then unzip and then upload. Then you know the files are clean.
Review the security of your addons and make sure that your addons come from official places. Consider to turn addons off for now.
There are a few solutions for running a virusscan on your server. Ask your host to help out.