What is a firewall?

A lot of people use firewalls, but what are they?

Perhaps the word firewall is confusing; this is because a firewall is more like a door than a wall.
As you walk down the street and look at front doors, you will notice that some are strong and others weak.
Some doors just need a kick and they will open.
Others are made of thick UPVC with multiple deadlocks.

This analogy is similar to the different types of firewalls that are on the market.

SOFTWARE FIREWALLS.
In my opinion these should NOT be used as your only defense.
They are very easy to bypass and should only be used as a backup measure.
The reason they are not secure is that if the computer is compromised then the first thing to be attacked is the software firewall.

To illustrate how insecure relying on a software firewall can be;
I have been on computers where Norton Firewall has asked if Zone Alarm can access the internet.
Unfortunately Zone Alarm was not installed on the PC.
Some programs pretend to be software firewalls so that they can gain control of the PC.

I would equate a software firewall to an internal door with a lock.
It stops the casual passerby from looking in, but if someone wanted to break in it wouldn't stop them for very long.

HARDWARE FIREWALLS
There are many types of these.
Some cost only a few pounds and others cost thousands.
Why the difference in cost.
The same reason why front doors range in cost.
The more you pay, the better they are.
I would look at paying about £100.
It seems that the £100 mark is usually a safe bet.
I have listed the things to look out for;

• NAT - This allows more than one computer to access internet at once and gives basic protection



• SPI - Stateful packet inspection - This looks at the information and does basic checks on it



• Blocking ICMP - Stops other computers from seeing that you exist on the internet



• DOS Protection - Denial of service - This is not so important, but it might stop someone from knocking you offline

This is only a basic explanation of firewalls, but I hope it helps.

My last piece of advice is this.
A good firewall has to be configured to allow internet services to work. If it just works without much setup then it probably has its settings to low.
A good firewall will shutdown connections to the internet when attacked, a bad firewall will open all connections when attacked.