In IIS is very easy to hide folders from HTTP browsing, this means that all the files and subfolders won't be accessible from the URL.

<configuration>
   <system.webServer>
       <security>
          <requestFiltering>
               <hiddenSegments>
                   <add segment="My_Directory" />
               </hiddenSegments>
           </requestFiltering>
       </security>
   </system.webServer>
</configuration>