New User Flood
That's true. I would do it, but I don't have shell access. So we have to wait for one of the senior admins.
Account creation temporarily disabled while I investigate what the best solution will be (starting with taking a close look at the server logs from the bad attempts)
Account creation is re-enabled.
I removed reCaptcha but in exchange made the math question slightly trickier. I also obfuscated the input field name to be a random string, and added two decoy fields like you mentioned Chase. One decoy is also named with a random string of the same form as the real one (and the ordering in the DOM is swapped at random), and the other decoy has the fixed field name that is normally used for a math captcha on Mediawiki.
We'll see if this keeps them out.
While I was at it, I also cleared out inactive users with a maintenance script.