Which logs are you referring to? The files creation date was Jan 26, 2011.

Server access logs.

You mean the IIS log files? I don't run Apache, remember? I still have all the log files, but have no idea what to look for, or even where to start, since I really don't know when the problem even started...as I believe I mentioned above.

This is what you might not understand - Even though vB.org is the "Official Modifications Site" for vBulletin, they do not (that I know of) themselves officially release any modifications, and do not inspect the ones which are posted here.

The community sometimes catches malicious code in some of the Mods that get posted here. Some others no doubt, escape any scrutiny.

I know that. vBulletin refuses to support hacked boards at all. But as mentioned, I have not installed any hacks since 2010, and before that one, 2008. (Which is probably the last time I updated. It would've been whenever 3.8.0 was released.) What you're insinuating makes no sense, since the creation date of the file is Jan/2011. I appreciate any help or ideas, but please don't sidetrack the topic. All hacks were installed and running smoothly LOOOOOONG before this problem existed.

Find out who has FTP access to your server and start from there.

I understand all of this.

I brought up styles because I do know of one that did have such a malicious file in it, that stayed dormant for months before going active. Wasn't saying definitely that such a malicious file existed in any of your mods or skins, or even insinuating it - was just, again, applying Occam's Razor. Spitballing.

I host my own server from my home. Nobody has any access to anything except the forum itself. There is no need for FTP when your server is right beside you. Direct access here only. All ports closed except 80, and I am behind two routers and a SW FW. That is about as secure as it gets, wouldn't you think?

[OT] Is that Jim Morrison in your avatar? Man, I love MR. MOJO RISIN!!![/OT]
--------------- Added 27 Nov 2011 at 13:40 ---------------

I see. I only have two styles (not counting vB default), and nobody uses the one that I don't have set to default. It's been that way since day 1. I created my own style and did install some, but never got them the way I wanted, so got rid of all of them. But that too was a very long time ago. At the time, there were not even updated styles for the version.