If you want to get a handle on comment spam on your Movable Type Pro or MTOS blog, one of the best things you can do is add reCAPTCHA to your comment form. The steps involved are fairly simple, but your reCAPTCHA configuration will fail if you miss a step.
The first thing to do is download the reCAPTCHA plugin and install it in your MTOS plugins directory.
After installing the plugin, go to Tools > Plugins in your blog and add your reCAPTCHA public and private keys. These are obtained by signing up for a free reCAPTCHA account.
Next you need to modify your comment form template. If you use the default templates in MTOS, this will simply be Comment Form, otherwise it will be whatever template you used to create your comment form.
Look for the code:
Replace this line with the following:
The final step is to enable CAPTCHA for your blog and rebuild. Go to the Preferences > Comment page and choose reCAPTCHA from the CAPTCHA Provider dropdown list. Save Changes and rebuild your Entry pages to enable reCAPTCHA across all posts.