The original MyDoom Virus installed itself on over five million computers and used them all to launch a Denial of Service attack against the SCO website. The virus was able to do this because the owners of those computers did not protect their computers with a firewall. The virus spread so quickly that many of these computers may have been running antivirus software but the software was not updated in time to recognise the virus. Had the computers been running a firewall they would not have been able to participate in the DoS attack even though they were infected with the virus.
Running any computer connected to the internet today without using a firewall is just plain irresponsible as doing so is effectively making your computer available to whoever wants to make use of it for whatever purpose they choose.
It is not even as if it costs anything except a small amount of time to install a firewall on your system. Windows XP even has a firewall built in that you can use if you don't want to spend time downloading a more sophisticated one.
When you have a stand alone computer that uses a dial up connection to the internet then using one of the free firewalls that can be downloaded from the internet should be quite sufficient to protect your computer from being used as a remote base of operations for persons unknown. There are a number of free firewalls available including:
If you have a home network and use internet connection sharing to share a dial up connection to the internet across your network then the free versions of the firewalls will only work if you turn down the security that you apply to your internet access. This is better than no firewall at all but still leaves your system partly exposed. To be able to properly protect your network you will need to upgrade one of the above firewalls to the paid version or alternatively obtain a firewall/router combination to replace both the firewall and ICS.
If you have a permanent connection to the internet from either a single computer or a network then a paid for software firewall is the minimum option that you ought to be considering. If you are just in the process of setting up such a connection then you ought to be looking for a complete hardware solution that provides permanent internet connection, routing, and firewall all in the one piece of hardware.
This article written by Stephen Chapman, Felgall Pty Ltd.