Managing web spam (either a comment spam, forum spam or “bots” registering in your site) is very time consuming and will reduce the productivity on your other task. Putting CAPTCHA to your comment forms, registration & logins forms, contact forms, etc. is one way of fighting and to at least minimize these automated spammy things.

Here’s a list of 20+ free CAPTCHA scripts and anti-spam solutions & services you can use to provide first-level degree of protection from spam bots and possible real human spammers. Most of these anti-spam solutions supports many web applications and programming languages including but not limited to WordPress, Drupal, Joomla, PHP, Ruby on Rails, ColdFusion and many more.

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  Mollom

  Mollom is a web service that analyzes the quality of content posted to websites using a filtering technique based on the combination of content analysis and CAPTCHA challenges. It helps keep your site clean and on topic by automatically blocking comment spam, forum posts spam, contact form spam and fake user accounts.

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  Defensio

  Defensio™ is web service that provides superior security against threats targeting social media, along with improved management and control of content posted on any site. It provides real-time malicious content detection, profanity filtering, Facebook protection, URL category blocking, enhanced statistics and a new & improved API.

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  Ironclad CAPTCHA

  Ironclad CAPTCHA is a 3D objects based CAPTCHA where each object can be positioned, scaled, rotated and colored in random way. The user are then required to count the number of three given types in the picture to pass the test. There are additional objects that should not be counted, besides three types that should.

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  Secureimage

  Securimage is an open-source free PHP CAPTCHA script for generating complex images and CAPTCHA codes to protect forms from spam and abuse. It can be easily added into existing forms on your website to provide protection from spam bots. It offers several security features such as image distortion, random lines, and noise.

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  reCAPTCHA

  reCAPTCHA is a secure and accessible anti-spam web service which protects your site from comment spam, malicious registrations and other forms of attacks by using a CAPTCHA to ensure that only humans perform certain actions. reCAPTCHA comes in the form of a widget that you can easily add to your blog, forum, registration form, etc. In addition to protecting your site, reCAPTCHA also helps us digitize old books and newspapers.

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  Picatcha

  Picatcha is a usable and secure image-based CAPTCHA with the goal of making it easy for humans to read but harder for bots to crack. Like KeyCaptcha, it lets visitors click/touch on its CAPTCHA instead of text typing. You can also customize the CAPTCHA such as the number of images, image sizes, color and noise type.

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  KeyCAPTCHA

  KeyCAPTCHA is an innovative anti-spam solution that does not require any text typing. Instead of guessing images and text, KeyCAPTCHA offers visitors to complete an easy interactive task. You can also earn money by specifying social and commercial advertising shares in CAPTCHA on your website.

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  VouchSafe

  VouchSafe is a secure and accessible test designed to separate human users from bots, to help prevent spam and some kinds of online fraud. VouchSafe is the first image-based Human Interactive Proof that uses an Adaptive AI to generate challenges based on the way humans think.

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  Solve Media

  Solve Media is a privately held CAPTCHA service specializing in challenging users to prove they are human by having them type in the text of an advertisers brand name which they are calling type-in advertising. The user challenge is for skippable pre-roll advertising in which the user is given the option to type in a slogan of the current advertiser in order to stop the advertisement that would normally play before the content is allowed to start.

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  HelloCaptcha

  HelloCaptcha is another web service, anti-spam solution providing animated images CAPTCHA. The first generation of HELLOCAPTCHA botdetectors are animated GIF images. The animation gives an additional dimension (the time) to the cracking algorithms.

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  Ajax Fancy CAPTCHA

  Ajax Fancy CAPTCHA is a jQuery plugin that helps you protect your web pages from bots and spammers. It has intuitive way of completing “verify humanity” tasks by asking user to drag and drop specified item into a circle. CAPTCHA’s security level is medium, with the emphasis on nice looking and user friendly qualities while still offering reasonable protection from unwanted “guests”.

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  NuCaptcha

  NuCaptcha is specifically designed to allow authenticated humans to pass quickly and easily while adjusting to a higher level of CAPTCHA security when a risk is detected. NuCaptcha uses measure indicators to identify suspicious, high risk activity and adjusts to present a real-time adaptive CAPTCHA.

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  Confident CAPTCHA

  Confident CAPTCHA is a clickable, picture CAPTCHA that stops spam and bots on blogs, web forms, account registrations, ticketing sites and more by asking visitors to click on specific pictures. It is highly customizable and administrators can increase or decrease the difficulty of the CAPTCHA depending upon the level of security needed.

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  textCAPTCHA

  textCAPTCHA provides a web service to generate textual CAPTCHAs based on simple logic questions. Instead of hard-to-solve image CAPTCHAs, textCAPTCHA uses textual questions which will serve as an initial barrier from comment spam, forum spam or “bots” registering in your site.

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  Sweet Captcha

  SweetCaptcha is a free CAPTCHA service with new and fresh graphical CAPTCHA focused on enhancing the user experience on your website. Instead of using difficult and boring text, SweetCaptcha offers a cute and interactive friendly user experience by letting users drag a picture into another picture.

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  ASIRRA

  Asirra (Animal Species Image Recognition for Restricting Access) is a human interactive proof that works by asking users to identify photographs of cats and dogs. It’s powered by Petfinder’s over three million images of cats and dogs, manually classified by people at thousands of animal shelters across the United States.

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  BotDetect CAPTCHA

  BotDetect CAPTCHA is feature-packed security solution using CAPTCHA challenges to prevent automated page posting. It allows you to have custom CAPTCHA image size, format, color scheme; custom CAPTCHA code length, style, character set, timeouts, generated code filtering and many other options & features.

WordPress Anti-Spam Plugins

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  Antispam Bee

  Antispam Bee protects blogs from ping and comment spam with sophisticated techniques. It can review the comment contents for BBCode links, block comments from specific countries, validate the IP address of commentators, allow comments only in certain language and many other advanced features.

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  Growmap Anti Spambot Plugin

  This anti-spam plugin will add a client side generated checkbox to your comment form asking users to confirm that they are not a spammer. Because the checkbox is genereated via client side JavaScript that bots cannot see, it should stop 99% of all automated spam bots.

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  Akismet

  From the creator of WordPress, Akismet is a hosted service to stop trackback and comment spam. When a new comment, trackback or pingback is added to your site it is submitted to the Akismet web service which runs hundreds of tests on the comment and returns a thumbs up or thumbs down.

7 More CAPTCHA Scripts and Anti-Spam Solutions & Services

1. The Honey Pot Metod:
   • Easy Spam Prevention Using Hidden Form Fields
   • PHP Honey Pot Spam Prevention
2. hOOmanTest
3. WebSpamProtect
4. adcaptcher
5. minteye
6. Captchator
7. Spamerator

Tags: anti-spam services, anti-spam solutions, captcha, captcha alternatives, captcha scripts, free captcha scripts, php captcha scripts, spam prevention, stop spam