Have you tried http://akismet.com/?
You can a free key if you sign up for a WP account.

First, you should get an email when you comment that allows you to approve your own comment. (That's the Comment Authorization plug-in at work.) I found your comment in the moderation queue while I was cleaning out all the spam comments — apparently there were two legitimate comments among the 3360 comments in the queue, and I'll update this post in a few minutes. This suggests to me that either you didn't get the email or I got about 370 spams in between your comment and when I started going through the queue. (For that matter, I had 49 new spams waiting for me when I got done.)

And Akismet has an insanely high percentage of false positives. We found this out on the Adium Trac; we started to have lots of wiki and ticket spam, so we installed the Akismet plug-in for Trac. Soon after, we started getting lots of bug reports by email because Akismet would reject their ticket submissions as spam. I don't know if there's any difference between Akismet on a Trac and Akismet on a blog, but this experience combined with Akismet's secrecy regarding the exact operation of the plug-in (sense a theme here?) makes me very averse to using Akismet.

yipes, have you tried and been displeased with Spam Karma 2 and Bad Behavior? I'd recommend immediately installing both. :)

Spam Karma 2's wiki page is amusing — it's filled with spam, itself. ;) (Note to all MediaWiki administrators: You need to turn on login. Yes, even though it's a wiki. Either that or write some WP-esque spam-prevention plug-ins.)

My problem with both plug-ins is that they do not disclose how they work, which makes me leery of installing them. I don't want to install anything that will block a legitimate comment, and if I don't know what the plug-in does, it's hard for me to decide (1) whether it is likely to be effective and (2) whether it is likely to block any legitimate comments.

The introductory post for Spam Karma does provide plenty of information on how SK works, but that's SK 1.4; I don't know whether SK 2 does anything more, less, or differently, and I'm not interested enough to find out. Bad Behavior has no useful information at all — only that it does something or other involving HTTP headers.

I'm just starting to learn obj-c and cocoa, and I like your blog, so I'm subscribing.

Glad to hear it. :)

http://unknowngenius.com/blog/wordpress/spam-karma/
http://www.homelandstupidity.us/software/bad-behavior/

I'm just starting to learn obj-c and cocoa, and I like your blog, so I'm subscribing.