Fight Aging! suffered an aggressive comment spam attack last week that forced the hosting ISP to take the server down for a while. The problem with the version of MovableType that we were using (2.661) was that it will rebuild several static pages after each comment - so a few hundred comments over a short period of time will bury the server. The very useful MT-Blacklist was installed, but that particular version is no protection against unrecognized, new spam URLs.
There are numerous ways of dealing with this, but I decided to upgrade to the latest version of MovableType and MT-Blacklist. The anti-spam functionality is improved and I've configured the new software to deal with the rebuild problem. All comments issued to older posts are now held for moderation rather than being posted immediately. In addition - something I should have done a while back - I have shifted the location of the comment submission script to a new, non-standard location.
We'll see if all that helps. In the meanwhile, you folks shouldn't see any differences on the site - but do let me know if you run into anything that looks like an upgrade bug.