Blue Captcha is a powerful and customized captcha plugin that protects your WordPress site from unwanted spams and persons. The plugin is easy to setup and activate high protection against spammers, bots etc.
You can easily encode mailto and plain email address links on your WordPress site and hide them from spambots. Email Encoder Bundle is a free WordPress plugin that plugin works directly when activated. Simply install and activate it, after activation visit your admin area Dashboard -> Settings -> Email Encoder Bundle plugin option page and check where you want options to take effect like you can enable it on all posts, comments and text widgets. You can set it to automatically encode both mailto and plain email addresses links, you can set class for mailto links and there are few more useful options.
With WP Mailto Links plugin you can easily protect all email addresses and mailto links from spambots and being used for spamming. The plugin is easy to use and configure.
With new WordPress plugin called Comment Auto Blacklist automatically adds IPs of spam comments to comment blacklist settings field in your WordPress site.