None of the firewalls described in this chapter run on Windows. Regrettably, there is a lack of quality of firewall open source software for Windows. Because Windows code is itself not open, it isn't easy for programmers to write something as complex as a firewall, which requires access to operating system–level code. With the addition of a basic firewall in Windows XP, there is even less motivation for coders to develop an open source alternative. This is unfortunate, because the firewall included with XP is fine for individual users, but it isn't really up to the task of running a company gateway firewall. There are commercial options available for Windows from companies such as Checkpoint. However, even they are moving away from a purely Windows-based solution because of the underlying security issues with Windows. If you need to use a Windows-based firewall solution, you will probably have to go to a commercial firewall, as there isn't a good open source firewall for Windows. This underscores the limitations and issues with closed source operating systems.