Firewalls

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Firewalls

Summary
The rapid spread of home cable-modems and DSL has raised the specter of malicious attacks against home computers by hackers. The use of firewall software can protect a home system.

Home cable-modems and DSL connections are becoming much more common. They provide instant-on (no dialup waits), always-on (no automatic disconnects), and extremely fast services. The down-side is that they expose the home computer to possible attacks from hackers. The "denial of service" attacks against Yahoo and others was possible because of home (and school and business) computers that did not have firewalls.

Cable-modems and DSL

Cable-modems and DSL are functionally the same thing to the home user. Both use a digital signal to directly connect to the Internet.

The cable-modem uses your cable TV company's cable line (which is optical cable up to the point where it branches from the telephone pole or when it gets to the box outside your house). A coax cable is run from the outside box to your cable-modem (actually not a modem but rather a network signal adaptor) and then a telephone-like cable (RJ-45) goes to your computer's NIC (Network Interface Card).

DSL stands for Digital Subscriber Line and runs over the telephone company's phone lines. It allows you to use the same telephone line for voice and Internet at the same time. You must have a special "modem" that connects between the phone line and the computer similar to the cable-modem.

When you have a cable-modem or DSL connection, you are truly part of the Internet. Unless you install a firewall your computer is totally accessible to anyone who has your IP address. And just how do they get your IP address? Simple. IP addresses are just a series of numbers (e.g., 123.456.678.01) that uniquely identify each node on the Internet. The hackers run a program that "pings" all of the potential IP addresses and logs to a file any IP address to which it gets a response. Another program is then run against all the IP addresses in the log file to detect was is available at the "good" IP addresses. Once the hacker knows that you have an "open" system, he can take over your computer. He can add and delete files, he can plant viruses and "Trojan Horse" programs. He could wipe out all the files on your hard drive. He can read all your email and documents. And he can use your computer to launch attacks on other computers.

So, how do you know if you are vulnerable to a hacker attack? The best and easiest way is to use ShieldsUp from Gibson Research Corporation. This is a free service that Gibson offers (not a software package that you download). ShieldsUp will ping your IP address and then tell you about all the holes in your security or, if you are lucky, that you don't have any holes. It also gives a very good explanation of Internet seurity. To bypass their opening screens you can go directly to the ShieldsUp page.

The next thing to do is to go to the ZoneLabs site and download their free product called ZoneAlarm, one of the highest rated firewalls available.

PC Magazine September 19, 2000
Opinions: Inside Track By John C. Dvorak
I would like to say that Version 2.1 of ZoneAlarm is a tour de force of software. This product is perfect — and stunning. I can’t recommend it enough. If you have DSL or cable modems, you must run it. I would even recommend it to a dial-up user. Fabulous. Am I raving enough?

I recommend installing it by taking all their defaults: I did and it runs perfectly. It will load automatically when you boot your system and will display a little icon in the system tray that indicates when you are having Internet traffic. A message is displayed in a dialog box every time somebody tries to "ping" you. I received three to ten pings a day (after a week or so I told ZoneAlarm to stop notifying me of attacks). ZoneAlarm makes your computer invisible to the outside world. It will ask your permission whenever a program (such as Netscape) wants to cross the firewall. You have the options of saying "Always Yes for this software", "Yes this time only and ask again", and "No". To bypass their Zone Labs' opening screens, go to the ZoneAlarm download page.

Finally, run ShieldsUp again to prove to yourself that you are now invisible (and invincible) to the outside world.

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