If you do not want to expose apache2 to external network, and access only through localhost you can use the following configuration snippet.

Add/Update /etc/apache1/sites-available/000-default.conf with the following:

 <Directory /var/www/>
    Options Indexes FollowSymLinks MultiViews
    AllowOverride None
    Order deny,allow
    deny from all
    allow from 127.0.0.1
</Directory>