Usually spam comes from random IP addresses, but lately I’ve gotten a lot from 184.108.40.206 (supposedly somewhere in Panama or Mexico).
The Akismet plugin does an excellent job of catching comment spam, but I’ve grown tired of seeing this particular address over and over again in the spam queue, so I’ve blocked that IP.
If you have a similar problem, there are instructions in the WordPress Codex at Combating Comment Spam/Denying Access on how to do this.
Aside, I’ve been really busy lately and haven’t had a chance to make any new posts. Hopefully things will get back to normal (such as it is) in a few days.