ellbristow

Force all posts by users without Editor or higher role to be private.
This plugin allows you to give your post writers the ability to create and publish posts on your site that are only visible to 
the author, and to editors/admins, by forcing all their posts to be private.
Features:
<ul>
<li>Anyone who does not have the ‘edit_private_posts’ capability can only post private posts</li>
<li>Limit all posts, or only newly added posts</li>
<li>(Optional) Also force a post to have a specific category when posted</li>
<li>Editors, admins and Super admins (who do have the ‘edit_private_posts’) can see all posts, and switch them from private to public if required.</li>
<li>No Configuration!</li>
<li>Just Activate!</li>
</ul>
This is my first publicly released plugin… so I hope you like it. Let me know if you find any bugs!

ForcePrivate

Force all posts by users without Editor or higher role to be private

marcucci

This is a very simple plugin that will check to see if a visitor is logged in before allowed your WordPress site to be displayed. 
If they are not it will display the login page of your site. It will also add text on the login page to explain that the site 
required all visitors to login.

Password Protect Plugin for WordPress

Force all visitors to login before accessing your wordpress site and add a message on the login screen explaining that login is required.

ForcePrivate vs Password Protect Plugin for WordPress