Hi!
I have a small blog and haven't yet been hit hard by spam, although I had a couple of waves of comment spam. There was another one yesterday and I had some spare time, so I decided to add a simple verification image (like the large blog sites do, just not quite as fancy).
The hack requires changes to the skins (_feedback.php) and a b2evo file (comment_post.php) but should not be too complicated (10 minutes maybe) if you have some basic PHP knowledge.
I did check the forum here and did not find anything similar and think this is the right place to share, but please bear with me if this is old and boring stuff or entirely misplaced alltogether.
I posted instructions on my blog, so if you're interested, follow this [url=http://www.blueflash.cc/blog/index.php/main/2006/08/30/verification_code_b2evolution_php]link[/url].
Enjoy
Markus
This looks like a handy app. I can't believe nobody has made this before, or included it as a plugin or standard feature in B2. One problem, I don;t think it will work with 1.8 and higher, or it needs different installation instructions. I tried to follow your directions but the feedback.php file is different in version 1.8 of B2.