パッケージ: libcgi-application-plugin-captcha-perl (0.04-2)

module providing CAPTCHA support in CGI::Application

CGI::Application::Plugin::CAPTCHA allows programmers to easily add and verify CAPTCHAs in their CGI::Application-derived web applications. A CAPTCHA (or Completely Automated Public Turing Test to Tell Computers and Humans Apart) is an image with a random string of characters. A user must successfully enter the random string in order to submit a form. This is a simple (yet annoying) procedure for humans to complete, but one that is significantly more difficult for a form-stuffing script to complete without having to integrate some sort of OCR.

CAPTCHAs are not a perfect solution. Any skilled, diligent cracker will eventually be able to bypass a CAPTCHA, but it should be able to shut down your average script-kiddie.

When a CAPTCHA is created with this module, raw image data is transmitted from your web application to the client browser. A cookie containing a checksum is also transmitted with the image. When the client submits their form for processing (along with their verification of the random string), captcha_verify() generates a checksum of the verification string the user entered. If the newly generated checksum matches the checksum found in the cookie, the CAPTCHA is assumed to have been successfully entered, and the user is allowed to continue processing their form.