WP Hotlink Protection a plugin by christopherross is a single step script designed to stop others from stealing your images. Simply add an .htaccess file to your root folder thereby stopping external web servers from linking directly to your files.
The script automatically tests to to see if your web server is compatible with the script before adding the .htaccess file and setting the appropriate permissions. If deactivated, the script removes the code from your .htaccess file.
The author says: This plugin works only with the primary domain, and the www. addition not subdomains.
Download and info: http://wordpress.org/extend/plugins/wordpress-automatic-image-hotlink-protection/
