Captcha is an important plug-in if you want to protect your site from non- human assault. Joomla has several captcha plugins which can be used for the same purpose. There are plugins which add recaptcha to your user registration page and contact page. There are separate captcha options for forgot username or forgot password options. These come with auto language detection as well as auto SSL. They have a few basic templates which can be easily tweaked with. Custom error messages can also be added when wrong captcha code is entered by user.
Most of them also support Ajax mode. Some of these captcha plugins are more advanced as they allow you to add colors, background images, signature to background images and other important security features like image distortion, noise and scratches. In case of difficulty in reading a captcha code the users can be presented with audio codes in Wav formats which are also a natural alternative which can be customized. They also provide high levels of anti-spam protection at different levels, which may include one or all among social ads, monetization through commercial ads, and simple protection without ads. And the level of security has been reinforced by the new era plugins which offers mini-games instead of simple word, alphanumeric codes and audio files. They have multi-language support as well, and the most commonly supported languages include English, Dutch, Portuguese, Italian and Spanish. Most importantly, some of the captcha plugins for Joomla also support manual entry of IP blacklist or whitelist.Cleantalk. Spam protect plugin for Joomla