we got around 4000 spam comments daily. Spam comments are increasing daily. when we fed-up these comments, we deiced to use the Akismet plugin. That is not enough. So Here is a list of unique and best wordpress comments captcha plugin
wordpress comments captcha plugin
I recomend to use the capcha plugin for protecting from spam comments. I like the wp-recaptcha wordpress plugin and I recommend to use that plugin.
Here are some very nice wordpress capcha plugins for wordpress comments.
WP-reCAPTCHA
reCAPTCHA is an anti-spam method originating from Carnegie Mellon University which uses CAPTCHAs in a genius way. Instead of randomly generating useless characters which users grow tired of continuosly typing in, risking the possibility that spammers will eventually write sophisticated spam bots which use OCR libraries to read the characters, reCAPTCHA uses a different approach.
Raz-Captcha
Prevent registration spam and bots login by adding custom captcha tests in the registration page and/or login page
Featuring 5 different and customizable captcha algorithms with possibility to set your own random characters font, styles, colors background and more
For a working demo se login and register pages from the author home page
Simple CAPTCHA
A CAPTCHA for your comment system to prevent unwanted spams. Prevent automated spams by bots and most important naughty peoples. It’s simple and yet secure.
WP Captcha-Free
WP Captcha-Free blocks automated comment spam without resorting to CAPTCHAs. It does so by validating a hash based on time (and some other parameters) using AJAX when the form is posted. Comments posted via automated means will not have a hash or will have an expired hash and will be rejected. Unlike using a captcha, this does not place any burden on the commenter.
CAPTCHA-Godfather
This plug-in protects the form for posting comments from spam by 4 ways; CAPTCHA code, Session ID (which is different from PHPSESSID), Timestamp, IP Address. Also allows the webmaster to choose between fonts.
Security Captcha
Prevent registration spam and bots login by adding custom captcha tests in the registration page and/or login page
SI CAPTCHA Anti-Spam
Adds CAPTCHA anti-spam methods to WordPress on the comment form, registration form, login, or all. In order to post comments or register, users will have to type in the code shown on the image. This prevents spam from automated bots. Adds security. Works great with Akismet. Also is fully WP, WPMU, and BuddyPress compatible.
I appreciate your sharing this information. I’ve been using simple captcha, but it’s really hard to read the numbers and gets very annoying. It also appears lately that the comments are going through anyway on the first shot. Someone who fails and tries again 2-3 times, I get the comment to approve or disapprove 2-3 times.
I like your site, but boy, is it hard to read with your tweet, buzz and stumbleupon, digg box here on the left hand side. Scrolling up and down to see the beginning of the line almost forced me off the site without reading the whole article.
There is also NO captcha plugin called keypic