Conditional CAPTCHA for Wordpress

Conditional CAPTCHA currently supports spam filters like TypePad AntiSpam and Akismet.

Installation:

Unpack and upload it to the /wp-content/plugins/ directory.
Activate the plugin through the 'Plugins' menu in WordPress.

Features:

• If a spam detection plugin identifies a comment as spam, it will ask the commenter to complete a simple CAPTCHA.
• If they fail, then the comment will be automatically discarded or trashed (and won't clutter up your spam queue).
• If they pass, it will be allowed into the spam queue (or approved, if you so choose).
• Meanwhile, genuine commenters (i.e., those not flagged by Akismet) will be able to comment on your site hassle-free.

What is new in this release:

• Fixed handling of array inputs that other plugins might inject into the comment form.

What is new in version 3.7:

• Added support for the new No CAPTCHA ReCAPTCHA.

What is new in version 3.6.3:

• Fixed PHP warnings on CAPTCHA page when other plugins have injected arrayed content into the contact form.

What is new in version 3.6.2:

• Allow line breaks in custom prompt message.

What is new in version 3.6.1:

• Added CSRF protection to settings page.

What is new in version 3.5:

• Changed logic to give priority to WordPress' built-in discussion options (especially moderation keywords/blacklist).

What is new in version 3.4.2:

• Added HTTPS compatibility for ReCAPTCHA.

What is new in version 3.4.1:

• Bugfix: make sure that WordPress can set commenter cookies when a CAPTCHA is completed correctly.

What is new in version 3.2.6:

• Doesn't intercept comments submitted via AJAX.

Requirements:

• WordPress 2.8 or higher
• PHP 5 or higher