Really Simple CAPTCHA

The CAPTCHA can be added from the Contact Form 7 interface by generating a CAPTCHA tag.

For stand-alone usage, a programmatic API is also available.

Installation:

Unpack and upload it to the /wp-content/plugins/ directory.
Activate the plugin through the 'Plugins' menu in WordPress.
Go to the Contact Form 7 settings page and add a CAPTCHA tag to the desired form.

What is new in this release:

• Removed spaces from response automatically as some users misthink there are spaces between letters.

What is new in version 1.5:

• The required WordPress version changed to 3.2 and higher.
• Use plain text file as answer file (again). This time, hash value generated with hash_hmac() is stored in the file.

What is new in version 1.3:

• Uses plain text file as answer file.

What is new in version 1.2:

• File name sanitization added.

What is new in version 1.1:

• The required WordPress version changed to 2.8 and higher.
• cleanup() method added.

Requirements:

• WordPress 3.5 or higher
• Contact Form 7 WordPress plugin