Apache allows to disable directory listing using htacess files.
By default in ubuntu apache document root directory is /var/www
you can edit configuration file located at /etc/apache2/sites-enabled/000-default
You have a folder called "private" in /var/www/private which contains some information. If your system is connected to internet and have public access anyone can get data from http://yourdomain.com/private !!
To disable directory listing try this:
create a file called .htaccess in /var/www/private
set your favourite editor
export EDITOR=vim
sudo $EDITOR .htaccess
Options -Indexes #disable directory listing on current directory
or
Options All -Indexes #disable directory listing recursively
