CAPTCHA alternatives
If your web forms are getting spammed, and CAPTCHA isn’t a good solution, here are some possible alternatives.
- http://isc.sans.org/diary.html?storyid=1836
- http://softwareas.com/captcha-alternatives-and-end-user-attitudes
- I’ve taken to renaming our feedback pages, and then using robots.txt to prevent search engines from indexing their new names.
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