What is a firewall?

A firewall is like the security guard of a building. The security guard screens people going in and coming out of the building, trying to prevent suspicious people from entering or thieves from leaving. In the same way, the firewall tries to stop suspicious data, such as viruses and worms, from entering your computer. It also attempts to prevent data such as your credit card numbers and passwords from being stolen from your computer.


Why do I need a firewall? (Why isn't an anti-virus programme enough?)

When you leave your house, you lock your doors and windows but even then, thieves may break your windows to gain access to your house. With a security guard, the thieves will have to get past the security guard first before he can even try to break your windows. Similarly, there are many other computers on the Internet trying to gain access to your computer. This is called probing. Installing a firewall makes it harder for the other computers to know if your computer has a "window" that can be broken into.

Also, the firewall prevents other computers from stealing data, such as your credit card numbers and passwords from your computer. Imagine that a thief has broken into your house and stolen some things from your house. A security guard would be able to stop the thief from running away with your things. Similarly, a firewall protects your data from being stolen.

How do I use it? (To allow or disallow?)

Just like telling the security guard who we trust and allow into our building, we have to tell the firewall what kind of programmes can go out into the Internet and who can read data from our computer. When a new programme tries to accept data from the Internet or send data out to the Internet, the firewall will prompt and ask if we allow the programme to either send or receive data. We can then tell the firewall if we allow the programme to access the Internet. The prompts from some popular firewalls are shown below:

Some simple questions you should ask yourself when deciding whether a programme should be allowed to send to or receive data from the Internet are as follows:

  		• Did my firewall prompt me after I have started a programme ?
  		• Is the programme I am running used to access the Internet?
  		• Does the programme require data from the Internet in order to work properly?

    If you answer 'yes' to the questions above, you most probably want to allow the programme to access or receive data from the Internet. If you are still in doubt, deny the programme access to and from the Internet and seek professional help through your software customer support staff.

    How do I reduce the number of prompts?

    If you run the same programme multiple times, the firewall might ask you many times if you want the programme to access the Internet. A possible solution is to use the feature of the firewall to either always allow or always disallow access by the same programme . This way, the next time you run the programme, the firewall will no longer prompt you in the future.

    Where can I get firewall software?

    Windows XP comes with its own firewall. You will need to turn on the firewall through the control panel. Seek professional help through Microsoft Helpdesk regarding configuring Windows Firewall. Other firewall software is either available through Infocomm security service providers such as Symantec, McAfee and TrendMicro. They can also be downloaded from the Internet. Popular firewalls such as ZoneAlarm can be downloaded from Internet.


    ZoneAlarm Pro Personal Firewall
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    Norton Personal Firewall
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    Mcafee Firewall Plus
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