This is one way of protect Website files, Directories and  images by hacking.If we have disabled listing files, nobody can able to view your potentially sensitive web site files on webpage. If directories listing is not secured it will allow users to access information very easily Therefore they can investigate the web server and hacking the website.

Disable directory listing:
If you want to  disable the directory listing on browser, create  a .htaccess under your website root directory or if the file is already existing  open it and add the below text line
Options  - Indexes
Enable  directory listing :
To Enable the directory listing on browser just open the same file  and replace “Options +Indexes” line instead of Options –Indexes.
Options +Indexes   (or)
 IndexIgnore *
Disable files with specific extension:
Ignore listing files on browser at certain file extension, it will be done by IndexIgnore, I  have decided will not listing file formats are .gif, .txt, .gar.gz.
IndexIgnore *.gif *.txt *.tar.gz
Disable directory browsing using httpd.conf:
My suggestion is that we have to configure in server end to get more secure will effect all VirtualHost, If you are using apache web server you can easily disable the listing directory by httpd.conf file. If apache server installed under the /usr/local/  open the httpd.conf file under conf directory like,
# cd /usr/local/apache/conf/
# vim httpd.conf

      Like, Options ExecCGI FollowSymLinks Indexes IncludesNOEXEC SymLinksIfOwnerMatch  then remove word Indexes and save the file after changes,
<Directory "/usr/local/apache/htdocs">
    Options ExecCGI FollowSymLinks IncludesNOEXEC SymLinksIfOwnerMatch
    AllowOverride All


Finally, restart the apache server
#  /etc/init.d/httpd restart
Stopping httpd:                                            [  OK  ]
Starting httpd:                                             [  OK  ]

The directory browsing feature should be disabled.