Want to secure your WordPress blog comment form? Want to an anti-spam measure to your other online forms (registration form, login form etc.)? If yes, going for a good CAPTCHA plugin is probably the simplest solution. There are many good CAPTCHA WordPress plugins and one of them is SI CAPTCHA Anti-Spam. This easy to use plugin can prevent spam from automated bots. It works great with Akismet and is also compatible with WPMU and BuddyPress.

Like other CAPTCHA plugins, SI CAPTCHA Anti-Spam displays randomly generated image codes that users must type correctly in order to submit a form. SI CAPTCHA also supports Section 508 and WAI accessibility validation. It generates audible CAPTCHA files in WAV format so that people with disabilities can easily enter the correct code. For changing the image code, a refresh button is also provided.

SI CAPTCHA comes with an options page where you can easily modify and update various options. You can specify where exactly your CAPTCHA should appear. You can add it to login form, register form and comment form. You can also set it to hide the CAPTCHA from logged in users and or blog admins. SI CAPTCHA supports i18n language translation. It means international users may use a translated version of their choice. Right now translations are available in 23 different languages.

Download link for SI CAPTCHA WordPress Plugin:

http://wordpress.org/extend/plugins/si-captcha-for-wordpress/