The spam has gone exponential.
I have just shut down comments on all but the last five blog entries. And I am switching off the ability to post comments globally for 24 hours. Normal service will be resumed tomorrow, i.e. on Saturday 17th around 4pm GMT (lunchtime if you're in New York). I am crossing my fingers and hoping that the shutdown will cause the spambots to give up and go away. It's a forlorn hope, I know, but it's worth a try.
If you're wondering what the 500 Server Errors are about, or why comments are currently closed, it's because the spam was coming in so thick and fast that the blog software couldn't classify it and bin it fast enough. None of it is getting through (it's really simple-minded stuff and easy to auto-detect and shitcan) but it clogs up the server's CPU and disks. In particular, this blog runs on Movable Type and MySQL, and has a dual-core 2.4GHz Athlon box to run on — about half the power of my last laptop. And it is being hammered. The trash can auto-empties after 30 days (yes, Alan, I tweaked the threshold) and currently holds a whisker under 59,000 spams; however, all but about 1-2000 of them have come in the past two weeks.
(If you want to contact me wrt. spam filtering, try tweeting to @cstross. Note, however, that I've been running this system for more than six years, I have expert help, and I think we've explored most of the options for securing a movable type installation.)