reCAPTCHA is a Google service that helps avoid automated ('bot) spam submission.

A CAPTCHA is a program that can tell whether its user is a human or a computer. You've probably seen them - colorful images with distorted text at the bottom of Web registration forms. CAPTCHAs are used by many websites to prevent abuse from "bots," or automated programs usually written to generate spam. No computer program can read distorted text as well as humans can, so bots cannot navigate sites protected by CAPTCHAs.

http://en.wikipedia.org/wiki/reCAPTCHA
http://www.google.com/recaptcha

VWcms supports the reCAPTCHA service for its three methods of information submission, $$COMMENT$$, $$FEEDBACK$$ and $$FORM$$.  Once configured (see below) all that is required is the inclusion of a $$RECAPTCHA$$ directive with appropriate parameter(s) on a page prior to the submission form and the reCAPTCHA dialog** will be added to the submit button.  This then must be completed correctly before the submission is accepted.

^**The default Google reCAPTCHA dialog mid-2011

For example $$RECAPTCHA$$ and its synonym $$RECAPTCHA$before=submit$$ on a page adds a reCAPTCHA dialog immediately before the submit button and $$RECAPTCHA$after=submit$$ adds the dialog immediately after the submit button.

Mailhide

Google also provides the Mailhide service which helps protect published email addresses by asking people to solve a reCAPTCHA before they can access the usable address.

http://www.google.com/recaptcha/mailhide/

The $$RECAPTCHA$mailhide=address$$ with optional parameter displays a link with an obscured address.

For example (non-functional), $$RECAPTCHA$mailhide=mark.daniel@wasd.vsm.com.au$$ provides ...@wasd.vsm.com.au and $$RECPTCHA$mailhide=mark.daniel@wasd.vsm.com.au$display=Mark Daniel$$ provides Mark Daniel.

Clicking on the link displays a pop-up dialog containing a reCAPTCHA that once solved displays another link with the visible and usable email address.

Configuration

reCAPTCHA requires a Google account and a set of keys.  Details can be found at the Google reCAPTCHA site.

VWcms must be provided with the site's public and private key (non-valid examples shown).

# VWCMS.CONF
[recaptcha-public-key]  6LeoO8JSABAAAMJagCq9KnILgSyjKpjvK6uKbwQx
[recaptcha-private-key] 6LeoO8JSABAAAKmKiD78I3I5fsZ6GRLA5F3Arcmy

Similarly Mailhide must be provided with public and private keys (non-valid examples shown).

# VWCMS.CONF
[recaptcha-mailhide-public-key]  012QFmC7cR9NSsMrNixjVSEA==
[recaptcha-mailhide-private-key] 3a0dc42089ec7c5f625004acb6db5616

reCAPTCHA can have theme and language customisation applied.

http://code.google.com/apis/recaptcha/docs/customization.html

The described options are configued using the [recaptcha-options] directive as in the following example.

# VWCMS.CONF
[recaptcha-options]  theme : 'white'

There are also [lang-recaptcha] messages that can be customised.