You can use a modern, low-cost router as a "hardware firewall" so that your local network and computers cannot be accessed by unexpected Internet traffic. You also need a router if you want to share a single, low-cost Internet connection with multiple computers on your LAN. Affordable router solutions are available from several vendors. The purchase prices are low, but the features vary a lot. But before you buy a router, you should learn the issues or you might be spending a lot of extra time struggling to install and configure one to your specific needs. Here are some free movies that will make it easy for you to learn the important concepts: