Last month we chatted about cookies. This month, let's chat about something called a "firewall."

What's a firewall? It's a small program that stands guard between your PC and the big, bad world. It keeps you, your PC, and its information safe from all the bad guys out there by not letting them sneak in your PC's backdoor when you're not looking. Would you leave your house without locking the doors? Without a firewall, that's what you're doing to your PC.

Now, you folks that are using "dialups" to connect to the Internet need to be somewhat concerned about having a firewall, but not as much as the folks using cable-modem or DSL connections. It's the folks with the, "always-on," cable and DSL connections that are at greatest risk.

Yeah, I know, you've already got "print and file sharing" turned off and "Java and Active-x" turned off, also. Well, good for you. That takes care of four potential problems. Now, let's talk about the roughly 57,776 other "points of entry" on your PC that you may not even know are there. I'm low balling that number by the way. I've seen some instances where that number can go well over 100,000.

Getting nervous yet? You should be. Have no idea what I'm talking about? OK, I'll explain a bit.

I'm talking about "ports." All communication in a PC happens through ports. Ports are communication points where hardware and software talk to each other, also, where software and software talk to each other. Now throw the operating system into the mix and you see where these numbers start to add up. I'm not talking about parallel or serial ports that connect your different pieces of hardware. I mean internal soft ports like TCP, UDP, FTP, HTTP, HTTPS, POP-3, yadda, yadda, yadda. These ports are where a hacker will attempt to attack your PC and attach himself to it for fun and "games."

I'm sure you all remember the big flap about a month ago concerning the denial of service (DoS) attacks on big Web sites like Yahoo and e-Bay. This was done by hackers who were able to find PC's that weren't protected by a firewall. They were able to determine the I/P addresses of a bunch of PC's and plant a program called a "trojan" on those PC's. The trojan opens a communication link between your PC and the hacker's PC, AND - the best part - if it's done properly, you won't even know its there!

Now that the hacker has a way to talk to your PC, he can make it do whatever he wants just as well as you can. He can read your files, use your machine to do work for him, reformat your disks, steal your information, pretend he is you and cause all sorts of trouble. This is bad.

A good firewall can prevent ALL this by plugging up all those open ports and controlling who can talk to what. This is good.

Sorry, Mr. Hacker, you can't use my PC anymore. I don't want to be responsible for letting you cause problems for someone else. I'm getting a firewall.

There are some very good firewalls available for home users. They are easy to install, will configure themselves to your PC, and are fairly inexpensive. Some are even free. If you would like to consider adding this type of software to your PC, here are some firewalls and their Web sites for you to check out and see what you might like to try.

• Zonealert from www. zonelabs.com This is an excellent firewall and it's FREE. Just download and install it.

• BlackIce Defender from www.netice.com This is not a freebie but the cost is minimal (less than $40.

• Norton NIS from www.symantec.com This is a revamp of the old "ATGUARD" firewall. Undeniably the "best there ever was." It sells locally for about $69 (check for a rebate to bring the cost down). Plus you also get Norton 2000 A/V with it.

• Mcafee Firewall from www.mcafee.com This is a subscription firewall. $39.95 buys you a year of use.

Lastly, I really don't expect anyone to take my word for all this so I'll give you two web sites that you can go to and see what the experts have to say.

• www.grc.com This is Steve Gibson's Gibson Research Center. Here you can do a little more light reading on firewalls and also do a test scan on your PC to see what is happening that you may not know about. It's free and very interesting. You can click on the "Shields up" banner and proceed from there.

• www.hackerwhacker.com  Bring coffee. You're gonna be here for a while. Lots of educational reading and some higher octane scan engines than on the Gibson site. Of course, more power equals more time.

These are both excellent web sites and are both very trustworthy. They will not harm your PC in any way and will not retain or sell any information about you.

Enjoy!