Many a times website owners edit or hack the plugin to change its default behavior. For instance, you edit the CSS of some widget plugin to match your website theme.
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 new WordPress plugin called Comment Auto Blacklist automatically adds IPs of spam comments to comment blacklist settings field in your WordPress site.
6Scan Security is a comprehensive automatic protection for WordPress based websites can get against hackers.The security scanner goes beyond the rule-based protection of other WordPress security plugins, employing active penetration testing algorithms for finding security vulnerabilities in a WordPress install. Then it fixes them then all automatically before hackers can exploit them. The plugin provides you regular updates to ensures your protection is always airtight.