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<tittel>Firewall in Windows XP</tittel>
<forfatter>atlegran</forfatter>
<sammendrag>WindowsXP has a built in firewall that is switched off by default. In this article you can read how to activate the firewall, and how to define which programs that are allowed to use certain services.</sammendrag>
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<avsnitt>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 <ekstern uri="http://en.wikipedia.org/wiki/Computer_bug">bugs</ekstern> on your computer. <uthev>NB!</uthev> The firewall does not replace <infoweb aid="364" tittel="Automatic update">security updates</infoweb>. </avsnitt>
<os2>Activate firewall</os2>
<bilde navn="firewall1" alt="Internet Connection Firewall" />
<avsnitt>Choose <uthev>Start->Settings->Network Connections</uthev> and right click the network connection you want to secure with firewall, and choose <uthev>properties</uthev> from the menu. This can be done on all types of connections. In the appearing window, choose the <uthev>Advanced</uthev>-tab and activate the firewall. Push <uthev>OK</uthev>, and your firewall will be active for this connection.</avsnitt>
<os2>Allow access to your computer</os2>
<bilde navn="firewall2" alt="Advanced settings" />
<avsnitt>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 <uthev>Settings...</uthev>. Push this button to open the <uthev>Advanced settings</uthev> 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 <uthev>OK</uthev>. This will open port 3389 in the firewall, and allow other computers to connect to this port. </avsnitt>
<os2>Logging</os2>
<bilde navn="firewall3" alt="Advanced settings" />
<avsnitt>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 <uthev>Advanced settings</uthev> window of your firewall (access as described above). Here you choose the <uthev>Security Logging</uthev> 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.</avsnitt>
<os2>Allow Ping</os2>
<bilde navn="firewall4" alt="Advanced settings" />
<avsnitt>In the <uthev>Advanced settings</uthev> window, choose the <uthev>ICPM</uthev> tab, and mark the <uthev>Allow incoming echo requests</uthev>. With this option marked, you can send a <ekstern uri="http://en.wikipedia.org/wiki/Ping" tittel="Ping">Ping</ekstern> command to your computer. This enables you to see the availability of your computer without logging on to it. </avsnitt>
<os2>Adding more services</os2>
<bilde navn="firewall5" alt="Service Settings" />
<avsnitt>The selection of default services offered by Microsoft is quite limited, but adding more services is quite simple. Open the <uthev>Advanced settings</uthev> window and click the <uthev>Services</uthev> tab. Click the <uthev>Add...</uthev> button, and a new window called <uthev>Service Settings</uthev> 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.</avsnitt>
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