So, somehow some pretty insidious malware got onto my site. From what I can tell it was installed via an old upload exploit in WordPress, on schadenfood.org (now offline since it's not like I was ever doing anything with it anyway). I did a bunch of forensics on it, and found that while the initial infection was probably just done by automated script, someone actually left a pretty thorough backdoor that allowed pretty much complete access to my whole Dreamhost account (files, shell, and so on).
Unfortunately, Dreamhost's logs don't go back far enough to find out how it was installed, and the backdoor script didn't keep a log so I have no idea what they did during the time leading up to the addition of the SEO spam crap that clued me in to its presence (because of a random happenstance that happened to make me aware that it had been installed at around 6 AM today). I have the IP address of the system that was used to access the backdoor, and I know that over the last few days they'd been accessing it repeatedly, but all of the commands are hidden in a POST request, so I have no idea what exactly they did.
I did go through and find every spot that they'd added additional exploit code, and of course I'm changing what passwords were visible in some way through the account files. Unfortunately, they had access to a couple of sensitive and important files that I was keeping in a private WebDAV share, and I'm feeling very sick to my stomach, especially with not knowing if they ever found the directory it was kept in. (I am, of course, moving all that stuff to my own personal NAS now, and deleting the WebDAV share.)
Fortunately, the only account password they'd have had access to directly was my database password, which I generate randomly and keep unique, and it's not a big deal for me to change it again. There's also a single spot where my OpenID password was viewable as an md5 hash (and it turns out that said hash is findable in some of the various md5 lookup tools out there), so of course I've changed that too.
HOWEVER: One of the bits of malware I dissected did appear to have the ability to generate a full table dump of my entire database (I don't know if this function was ever activated), and you should be aware that phpBB 2 (like I use here) uses unsalted MD5 password hashes. So you should probably change your forum password here, and anywhere else that you use the same password. Sorry. :( (I'd upgrade to phpBB3, which finally fixes that issue, except that it will break all of the commentary functionality on my site if I do. I should look to see if there's at least a salted-md5 patch for phpBB2 floating around out there though. I've been meaning to do that forever but of course now that's squeezing my buttocks after I've farted, as the Japanese saying goes.)
I have, in the meantime, removed ALL the goofy webservices that I'm not using anymore, and hoping that the ones I still do have installed (because I, you know, use them) are secure. I should definitely check for security updates on what's left, at least. Also, do a full audit on all of my custom PHP scripts because who knows what's lurking in those.
tl;dr: The site was hacked, your password may be compromised, and the hack was directly targeted enough that I'm feeling violated and am probably going to have my identity stolen or something now.