valcorin

For those who just want all users who aren’t logged in directed to the login page, you can modify the plug-in to the following:

<?php
/*
Plugin Name: Protected Site
Description: Block users from accessing your blog or a specific blog in your network by activating this plugin on the blog you wish to protect.
Author: Davo Hynds
Version: 1.0
Author URI: http://ashramcreative.com
Modification: Code modified to redirect to the login page rather than requiring a click through
*/

add_action( 'get_header', 'ac_protected_site' );
function ac_protected_site() {
	if ( !is_user_logged_in() ) {
		$bigurl = home_url().'/wp-login.php?redirect_to=';
		$path = parse_url(get_bloginfo('url'),PHP_URL_SCHEME).'://'.parse_url(get_bloginfo('url'),PHP_URL_HOST).$_SERVER['PHP_SELF'];
		$bigurl = $bigurl.$path;
		header( "Location: $bigurl" );
	}
}
?>