Disable Directory Listing Apache2

Edit the following file:

/etc/apache2/apache2.conf

Remove 'Indexes' from default root directory setting:

<Directory /var/www/>
Options Indexes FollowSymLinks
AllowOverride None
Require all granted
</Directory>

Updated apache2.conf file:

<Directory /var/www/>
Options FollowSymLinks
AllowOverride None
Require all granted
</Directory>

Restart the apache2 server instance.