A CAPTCHA is a program that can generate and grade tests that most humans can pass, but current computer programs can't pass (typically a picture with distorted text).
This module provides a validation service used by other modules such as for user login, new user registration, guest comments and sending eCards. This helps prevent spammers and hackers from using programs to automatically perform these operations.
Requires GD 2.x or newer support in PHP for image generation. Note that most PHP installations have the GD extension loaded.
PHP compilation tips: In addition to the GD library, PHP must have JPEG support enabled at compile time. Add these compile time flags when you build PHP.
--with-gd --with-jpeg-dir=/usr/lib (OR any other directory which contains the BINARY library of libjpeg)