WordPress is a most popular open source powerful blogging platform. That's why it has been a huge attraction to the hackers, robots, spambots and other unwanted exploits. Here 're some security plugins to protect your WordPress comment system:
- Akismet one the most useful securicty plugins. It checks comments in the blog against Akismet web service to check if they're spam or not.
- AVH First Defense Against Spam block spammers before the content is published by checking if the visitor's IP is listed in the database served by stopforumspam.com, Project Honey Pot or a local blacklist.
- Invisible Defender protects registration, login and comment forms from spambots by adding two extra fields hidden by CSS.
- NoSpamNX automatically adds additional form fields to comment form, invisible to human users. 99.9% of all spambots fill these fields and NoSpamNX willn't save the comment.
- WP Hashcash is an antispam plugin. It eradicates comment spam on WordPress blogs also prevents most trackback/ pingback spam.
- Spammer Blocker – tired of manually blocking spammers's IP addresses, this plugin blocks all visitors who posted a comment marked as a spam. For e.g. if Akismet catches a dummy bot who posted a spam comment, it'll be blocked until you approve/delete his post.
- Block Top Spammers displays a list of top spammers' IP addresses, based on comments in your database marked as spam. It also generates a blacklist for your .htaccess file to block those spammers from your website entirely, thus taking load off the server. You'll need another plugin (like Akismet) to identify spam.
- IntenseDebate Comments enhance and encourage conversation on your blog or website. Custom integration with your WordPress admin panel makes moderation a piece of cake.
- Disqus Comment System replaces your WordPress comment system with your comments hosted and powered by Disqus. Disqus, pronounced "discuss", is a service and tool for web comments and discussions.
Also, second part of this post detailing Best CAPTCHA WordPress Comment Security Plugins.