Spammed by gambling sites again while away. Interestingly, only some of the entries were hit this time, not all of them like before. Maybe it's because the bot wasn't as efficient this time around or maybe the IP banning actually worked. Added some more IP addresses just in case. Have also set "Allow comments" to "closed" by default and went back and closed comments on all previous entries. Only ever had one comment in all this time anyway, so no big loss. This blog may be publicly accessible but it's intended for an audience of one.
edit: On the other hand this timely article has persuaded me to upgrade to MT version 3.x.