You need to secure your network from people that try to gain access to your network through the Internet.
There are many ways to protect your network from being attacked by hackers or viruses. One way is to make sure your network is not attached to the Internet at all and you only have a few computers with access to the Internet, but not the network. This is one of the safest ways, but not convenient if you need to update your information on a website regularly.
Another way that is more favourable is to have a Firewall that will protect your network and allow your employees to be able to go on the Internet. What a Firewall does is it separates your intranet with the Internet.
There are many different types of Firewalls you can choose from to help protect your intranet. The technologies include the crypto-capable routers which encrypts certain information that you which to send on to the Internet and encrypts other files as well. A more popular way for companies to be able to send information on the main sites network to an off cite location is to use a virtual private network which uses the Internet to send information from the network to the off cite location by encrypting all the data sent.