This worked for me:
Inside the .htaccess file in the root directory, place the follow at the very top:
Upon a visitor accessing a folder with no index.html, they are sent to the root index.html, rather than being able to view a list of folder contents.Code:Options -Indexes
NOTE: A file within the folder CAN still be accessed by typing its complete path. (Example: mysite.com/images/picture.jpg)