Starting in Windows XP Service Pack 2 and all newer versions of Windows (Vista, Windows 7), Microsoft included a product called the Windows Firewall which allows you prevent everyone on the Internet from communicating with your computer.  We can use this tool effectively to help keep your X-Server from receiving unwanted connections, and thus reduce the number of times the dialogue box asking you to accept a connection appears.

On Windows XP with Service Pack 2 or above installed and the built-in firewall enabled, you can take further steps to reduce the number of unsolicited connection requests you receive.

To do so:

  1. Open the Control Panel folder via the Start Menu
  2. Double click on Windows Firewall (or access it via the Security Center control panel)
  3. Click on the Exceptions tab
  4. If you followed the instructions linked above, you have an X-Win32 program listed in the Program and Services section.
    1. If you have installed more than one version of the X-Win32 program on your PC (this happens when you upgrade) you may have multiple entries.  If you highlight one and click on “Edit…” (or double click the one you highlighted) it will show you the path to the application.  The path contains the version number.  You can delete entries for older versions safely.
    2. Once you’ve identified the correct entry, click “Edit…”
  5. A new dialogue box will appear. Click on “Change Scope…”
  6. Another dialogue box will appear, allowing you to configure the Internet addresses you wish to allow to connect to your X server. You do this by specifying an IP address range in the “Custom list” section. First, click the radio button next to Custom list. Then, supply the address range appropriate for your needs.For most people, allowing the 128.197.0.0/255.255.0.0 address space, which encompasses most of BU including ACS and all other central resources, will be sufficient. SMG users may need to use 168.122.0.0/255.255.0.0 instead of or in addition to the 128.197.0.0 range–separate multiple ranges with a comma.
  7. Click OK and this dialogue box will close
  8. Click OK to close the “Edit a Program” dialogue box
  9. Click OK once more to close the Windows Firewall box (and once more to close the Security Center if necessary).

Your PC will now refuse X server connections that do not originate from the specified local BU IP address range, reducing the number of times you get prompted to accept a connection you really didn’t want.