Stop bots from spamming : Old style CAPTCHA - Alternatives or replacements

Old style CAPTCHAs are pretty much broken. So what else we can use to replace it. Given below are some alternatives to old style CAPTCHAs.

1. reCAPTCHA - It is a free CAPTCHA service that helps to digitize books, newspapers and old time radio shows. They deliver CAPTCHAs that are proved to be unreadable by OCR and donate the human processing to a charitable cause, preserving out of copyright books for future generations.

2. CSS hidden field - Add a text input field to your form and give it a name that makes sense. Then with some CSS hide the table row or div that the input field is in. The bots should fill it in, add some code that checks that the hidden field was not filled in, and if you find this field filled in, you can quit execution right there. Make sure to label this so that people with screen readers can understand not to fill it in.

3. Work out the time that it took for the form to be submitted - In your form, add a hidden variable and set its value to the time stamp of when the form was loaded. Then, once the form has been submitted, get a new time stamp value and compare the two values. If the new value is less than say about 5 seconds (or the time you estimate it will take a human to fill in your form, remembering that spam bots will do it almost instantaneously) then you can return to the form with a error message stating that the form was submitted in too short a time period.

4. Give the user simple Challenge questions like - What are the total number of syllables in the American President's full name. OR, put a simple math equation at the bottom of the form like (2 + 4 - 1 =). Remember the fact that you would need to make the questions random.

5. Use music. Play the music and give the user multiple choice answers.

6. After filling the form have the users go to another link and copy and paste an constantly changing image into a box. This would be similar to an RSA token but without the hardware.

In the end, nothing is perfect but the end result is something that is accessible and will keep your site safe.