This plugin Adds Crazy Additional Password Protection and Security to your blog.
.htaccess Site Access Control plugin allows you to password protect your site: WP login page, admin pages, and/or the whole site.
Quickly and easily password protect a site to keep it from the prying eyes of google.
Simple, but strong HTTP security, to prevent Brute force attack. One-click solution!
HTTP Authentication lets you make a site without letting anyone view it without valid credentials. This can protect the full site or only admin pages.
Sync your WordPress users with .htpasswd file for enabling Apache (2.2.18 and above) basic authentication based on file for your resources
Convert your wordpress page or post to a security or encryption online tool generator.