There are many different modules like as Captcha, reCAPTCHA, Spam, AntiSpam etc.. For preventing form spam on your website, and an important component against spam is your constant struggle between giving your 'real' users a good experience while preventing spammers and automated bots from spamming you and lowering the quality of the content on your website? CAPTCHA uses complex code which is difficult for a normal person to read, it's even harder so for those with poor eyesight. In addition, many (if not most) CAPTCHA implementations are inaccessible to blind people or those using assistive devices to read your website.

I am going to explore about Honeypot, where user is given no extra effort to completing a form but prevent spam scripts to submitting the form.

Install and configure Honeypot

• Install the module Honeypot and enable it on /admin/modules page.
• Click on Configure link

  

• You will redirect on Honeypot configuration page(/admin/config/content/honeypot).
• Enable the checkbox for which you want to addd Honeypot. In my case, enable the Blog comment form

  

Honeypot method basically inserts a hidden form field to Drupal forms with a field name like 'url'. End users don't see the field, so they don't fill it out.

But spam bots (usually using prewritten scripts) do see the field (usually), and add something to it. The Honeypot module detects this and blocks the form submission if there's something in the field.

Additionally, the Honeypot module adds in a Timestamp-based deterrent. Usually, when a human is entering data into forms comment form, user registration forms, etc., they take at least a few seconds to fill out. However, spam scripts that want to post spam comments on hundreds of forms every second will try submitting the form within less than a second, and Honeypot will stop that from happening.

You can tell Honeypot to protect all forms on the site or only enable Honeypot for the forms you needed. you can also use honeypot protection in your own forms by simply including a little code snippet specified below:

<?php honeypot_add_form_protection($form, $form_state, array('honeypot', 'time_restriction')); ?>

The greatest advantage of the Honeypot method is that the user is given no extra effort to completing a form. In my opinion, it's the most user-friendly way of preventing spam, even if it's not the most effective in every situation. In those case you might need to add with Mollom or another more intelligent spam prevention service to the mix.