Mirror Magazine


Techno Page
By Harendra Alwis

Installing firewalls
Test drive
Once you have a firewall in place, you should test it. A great way to do this is to go to <www.grc.com> and try their free 'Shields Up!' security test. You will get immediate feedback on just how secure your system is!

If you have been using the Internet for any length of time, you have probably heard the term 'firewall'. For example, you often hear people say things like, "I can't use that site because they won't let it through the firewall".

"Basically, a firewall is a barrier to keep destructive forces away from your property. A firewall in computing terms is simply a program or hardware device that filters the information coming through the Internet connection into your private network or computer system.

For example, let's consider a network with hundreds of computers that are connected to each other and to the Internet. These machines will be connected with network cards and it may have a couple of high-speed internet connections. Without a firewall in place, all of those hundreds of computers are directly accessible to anyone on the Internet. A person who knows what he or she is doing can try to make FTP or telnet connections to them and so on. If someone makes a mistake and leaves a security hole, hackers can get to the machine and exploit it.

With a firewall in place at every connection to the Internet, it can implement security rules. For example, one of the security rules inside the company might be:

Out of all the computers inside this company, only one of them is permitted to receive public FTP traffic.

You can set up rules like this for your servers then you can control how others connect to Web sites, whether files are allowed to leave the network, and so on. A firewall gives you tremendous control over how people use the network.

Firewalls use one or more of three methods to control traffic flowing in and out of the network. They are:

1. Packet filtering - Packets (small chunks of data) are analyzed against a set of filters.

2. Proxy service - Information from the Internet is retrieved by the firewall and then sent to the requesting system and vice versa.

3. Stateful inspection - A newer method that doesn't examine the contents of each packet but instead compares certain key parts of the packet to a database of trusted information.

Firewalls are customizable. You can add or remove filters based on several conditions such as IP addresses, Domain names and Protocols.

A software firewall can be installed on the computer that has an Internet connection. This computer is considered a gateway because it provides the only point of access between your network and the Internet.

With a hardware firewall, the firewall unit itself is normally the gateway. You configure a router via a Web-based interface that you reach through the browser on your computer. You can then set any filters or additional information. Hardware firewalls are incredibly secure and inexpensive.

One of the best things about a firewall from a security standpoint is that it stops anyone on the outside from logging onto a computer in your private network.

While this is a big deal for businesses, most home networks will probably not be threatened in this manner. Still, putting a firewall in place provides some peace of mind. After all, what is a network with thousands of computers worth if you don't have peace of mind at the end of the day? Don't hesitate to write in and share your views.

You've got mail
Very often, you may receive emails that either warn you about a virus or simply urge you to forward a message to as many others as possible.

Some of these are malicious, and some are not, but almost all of them are pranks because they cause damage or loss to the rest of the Internet community in some way. This is true most of the time, not always. You may get a nice, touching message which insists that you forward it to twenty or thirty people.

If you want to do that fine, but doing it without any purpose causes Internet traffic to increase. Imagine what would happen if every email user started doing that.

For example, one person sends it to ten people, they in-turn send it to ten others and this keeps multiplying until it may gain enough momentum to clog the whole Internet! This may not happen practically all the time, but theoretically it could be quite devastating. So you can do your best not to get 'hooked on' to such silly habits.

The facts about virus warnings though, are a bit more serious. To begin with, go to the official web site of MacAfee, Norton or any other site of a reputed anti-virus expert and register with your email address to receive regular newsletters about the latest viruses. They provide authentic information about viruses and their cures, so you will have nothing to worry about.

Apart from that, do not trust any other email that tells you of a virus in your computer. If you get such a letter, first check to see whether it contains a valid link to an authentic web site maintained by an anti-virus expert and check to see if that link directs you to the relevant information. If it doesn't, just delete the email because chances are that the very email could have a virus attached to it!

One of the key features of these hoax warnings is that they urge you to inform everybody else in your address book about the threat of a virus. Some of them seem real because they tell you of the exact location of the virus within your computer and when you go there, you actually see a file with a 'funny' icon which you are made to believe is a virus and thus delete it.

These are mostly system files that are vital for the operating system to function properly and once deleted, you could be in serious trouble.

So as a rule of thumb, take another look at those emails that ask you to forward them to so many people, and analyze their contents. If it is something unimportant or if it is a virus warning, delete it. If not do whatever you want with it, but don't forward them to avoid bad luck or whatever they claim to bring with them because you could just be bringing bad luck to yourself and many others on the Internet by doing so.

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