This site has been up for less than a month and already hit twice with presumed automated spam. When these jokers hit your site it makes you feel kind of violated, like you left the back door open and then came in under your nose.
For a while now, I have seen those picture number validation controls and several blogs, used to prevent automated spam. I did not research the matter and figured it was yet another thing I could procrastinate put off until some time in the future.
The day after I was hit the second time with spam, I found that a site, which hosts another blog of mine, www.WDevs.com had run into the very same problem. Anders Molin, wrote an entry about adding the new validation control to break automated attacks to WDevs blogs.
I did a little digging and found the control Anders used called "Hip-Captcha". You can find (at this time) the latest version at:
http://blogs.clearscreen.com/migs/archive/2004/11/10/575.aspx
It was extremely easy to add to the ".Text" blog software used for this site. Only took a few minutes to be freed from automate spam on the site. While it is not that difficult to build one of these controls (I use one on HintsAndTips.com and on MyQuickPoll.com), the Hip-Captcha is a handy package, all ready to go!