If your web forms are getting spammed, and CAPTCHA isn’t a good solution, here are some possible alternatives.
- I’ve taken to renaming our feedback pages, and then using robots.txt to prevent search engines from indexing their new names.
- Related Link: http://kb.ucla.edu/articles/what-is-captcha
The Akismet service has a good reputation, and is widely used by Wordpress amongst others. It could be another layer of protection against spam.
- http://akismet.com/ (official site)
- http://codex.wordpress.org/Akismet (an example of it in a blogcentric CMS)
Jared Smith of WebAIM has compiled a series of server-side processing techniques that get rid of spam without the use of CAPTCHA. Scripts are provided in PHP.
The scripts include:
- Detect spam-like content within submitted form elements
- Detect content within a hidden form element
- Validate the submitted form values
- Search for the same content in multiple form elements
- Generate dynamic content to ensure the form is submitted within a specific time window or by the same user
- Create a multi-stage form or form verification page
- Ensure the form is posted from your server