You can limit access to the Apache server if you only want to use it internally (for testing purposes, to access the doc-central archive, etc..) and do not want outsiders to access it. To do this use the Listen or BindAddress directives in /etc/apache/http.conf.
Using Listen:
Listen 127.0.0.1:80
Using BindAddress:
BindAddress 127.0.0.1
Then restart apache with /etc/init.d/apache restart and you will see that it is only listening on the loopback interface.