Intranet question for gurus out there

[scrapplesauce]

I am setting up an intranet for a company, and im worried about security. They have 5 locations around the country that need to access the intranet. What are my options as far as putting the intranet behind the router and making it work with the other 5 locations around the country. What other options do I have? a URL with a walkthrough would be cool...

Let me know..