Firewall in Windows XP

The built-in firewall in Windows XP is switched off by default. If you activate the firewall, other computers will not be able to send information to your computer without your authorization. This means that you can connect to fileservers and web pages as usual, but that others who try to take advantage of potential bugs on your computer. NB! The firewall does not replace security updates.

Activate firewall

Choose Start->Settings->Network Connections and right click the network connection you want to secure with firewall, and choose properties from the menu. This can be done on all types of connections. In the appearing window, choose the Advanced-tab and activate the firewall. Push OK, and your firewall will be active for this connection.

Allow access to your computer

In the Advanced settings of the firewall you can define which services on your computer that should be available for internet users. If you have activated Remote desktop and want to access your home computer from the university or your workplace, you'll have to allow this kind of traffic over your network. In the window where you activated your firewall, there is a button marked Settings.... Push this button to open the Advanced settings window. In this window you can se various services that can be made available for external users. In order to enable remote desktop, you'll have to choose it from the list and click OK. This will open port 3389 in the firewall, and allow other computers to connect to this port.

Logging

Any computer that is connected to the internet will daily experience a series of connection attempts from other computers. This might be random mistakes or serious threats as hacker or virus attacks. If the amount of traffic directed towards your computer is very large, it might slow down the performance. To find out if decreased computer performance is due to increased traffic, you could check the log file generated by your firewall. The logging can be turned on in the Advanced settings window of your firewall (access as described above). Here you choose the Security Logging tab, and activate the logging. The log file will be saved in the location specified. The log file can be opened with a text editor such as Notepad or Textpad, and contains information about all attempts of sending information to your computer.

Allow Ping

In the Advanced settings window, choose the ICPM tab, and mark the Allow incoming echo requests. With this option marked, you can send a Ping command to your computer. This enables you to see the availability of your computer without logging on to it.

Adding more services

The selection of default services offered by Microsoft is quite limited, but adding more services is quite simple. Open the Advanced settings window and click the Services tab. Click the Add... button, and a new window called Service Settings appears. Here you write the name of the service you wish to add, the name of your computer, the external and internal port number. For instance, if you want to use remote desktop through a firewall that only allows traffic via port 80, you'll have to use port 80 as external port and 3389 as internal port.