Flex captcha can be used to secure login, contact form (or similar).
It can help you to prevent/reduce:
Automated sign-ups in registration forms.
Comment spam in blogs and guestbooks.
Brute force attacks on login systems.
Providing an audio CAPTCHA for accessibility reasons.
You can configure it at source code without use an xml file too.
The image used for the captcha is generated and validated using PHP .
All options configurable via XML (A sample XML is included).
You can easily integrate this application anywhere.
Source code commenting.
Requires PHP 4 .1 or above.
PHP session support is also required.