If your machine connects to the Internet, it really should have a firewall. If it’s connected to the Internet full-time, as with a cable modem or DSL, it really really should have a firewall. Most of the people who have fallen victim to snooping attacks from the Internet are people without a firewall.
Here are three ways to get yourself a firewall:
A router is an inexpensive box that distributes the signal from a single cable modem (or DSL) to one, four, eight, twelve, or more computers on your network. As a delicious benefit, most routers these days contain a built-in firewall. The beauty of a hardware firewall like this is that first of all, it’s always on, and second of all, it protects the entire computer simultaneously.
In the following paragraphs, you’ll be reading about software firewalls. But a hardware firewall is even better. Some people, in fact, buy a router even if they don’t intend to share the cable modem’s signal with other PCs—they get it just for its firewall protection.
In general, in fact, you can pretty much tune out of the following firewall discussion if you’re protected by a hardware firewall. That is, unless:
You’re on a small-office or home network. In this case, your router will protect your network from nastiness coming in from the Internet—but a software firewall can protect your PC from other PCs on your network. If little Timmy up in his bedroom downloads some virus-infested bit of file-swapware, ...