Why do you need a router?
You know how your phone rings and the voice on the other end urges you to vote for a candidate you don't like?
Know why that doesn't happen to you at work? It's because those who interrupt your dinner have the direct number to your home — whereas when they call your work number, they reach the receptionist, whose job it is to transfer only business-related calls to your extension.
In Geekspeak, we would call your home telephone number a "public address," even if it's unlisted, because anybody with a telephone can dial it directly.
We would call your extension at work a "private address" precisely because it can't be dialed directly.
A router works in the same fashion.
For the purposes of this discussion, a router is a device that allows two or more computers to share the same broadband Internet connection.
It does this by taking the role of the receptionist. It "answers the phone" when information is sent to your "public address" — and directs (or "routes") it to the computer which requested it, which has taken a "private address."
This process is called Network Address Translation, or NAT.
The reason this "protects you from the bad stuff" is that it eliminates all of the systems on the Internet which are scanning public Internet addresses looking for unsuspecting systems to infect; all they can detect at your "public address" is a router, and they move on.
So the only bad stuff that can get to your computer is the stuff you go out and find on your own.
You may already have this feature and not know it. Some broadband providers send you a modem with a built-in router when you first set up your account.
The easiest way to tell is to open a Command Window (press and hold the Windows key — the one with that little four-square flag on it, to the left of the spacebar — and type an "R". Then type "cmd" into the dialog box that appears and click on "OK").
A window will open with a black background and white letters, and the words "C:Documents and Settings\YourNameHere>" or something along those lines will show up.
Type "ipconfig" and press "Enter." In the results that spew out, look for the line that reads "IP Address."
Mac users are looking for the Terminal application (in Utilities), and the command is "ifconfig."
Internet Protocol (IP) addresses are displayed in "dotted quad" notation, which is Nerdspeak for "four numbers, each between 0 and 255, separated by periods."
If the first number is 10 (for example, 10.0.0.1) your address is private. If the first is 172 and the second is 16 through 31 (for example, 172.16.0.1) your address is private. If the first two are 192 and 168, respectively (for example, 192.168.1.1) — by far the most common sequence — your address is private.
If the numbers are anything else, you don't have a private address and should seriously consider getting a router.
You can find one online, at Staples or WalMart, or most home electronics stores. They will cost you somewhere between $20 and $160.
The most common manufacturers are Linksys, D-Link, Netgear and Airlink 101 — but there are certainly other brands which will work just as well.
Installation is simple. On most systems, you take the cable which connects your modem to your computer — it should have a connection on each end that looks like a telephone connector, but slightly bigger — and unplug it from your computer. Plug that into the "WAN" or "Internet" connection on the router.
Then take the cable that came with the router — it should have the same connectors — and connect one end to any of the "LAN" ports on the router and the other end into the hole in the back of your computer the first cable came out of.
If your router came with an installation CD, you will probably want to run the setup program on it before you move any cables. If it's not clear how it all hooks together, most routers come with a toll-free number for installation help.
Consult the manual (or ask tech support) how to change the password and disable the wireless feature (unless you have need of it — in which case you should make sure it's encrypted).
Information adapted from http://www.foxnews.com/story/0,2933,367705,00.html