I just saw a post on Life Rocks 2.0 which explains you to how to protect your wordpress theme files. It is possible for any one to see your wordpress theme files or plugin folders to see what themes you are using or what plugins you use if you don’t protect them.
What you do to protect, one method is to follow above linked post, but the problem is what to do when you have many directories with out index.html files. In this case adding a simple rule to your .htaccess will solve the problem.
Simply add “Options -Indexes” to your .htaccess file, so whenever try to open any directory on your webserver with out index.html file will show a 403 error page. With this one rule you can save lot of time in creating index.html files to each directory.
This only works with Apache Webserver. Read more about Options indexes.