netDefender

NetDefender firewall is a Free Firewall with source code which will be downloaded along with firewall. It works on windows 2000 and above versions of windows. It has a very easy to use interface. NetDefender Firewall is completely written in VC++ using MFC , Windows API, Filter Hook Driver (Provided with Windows 2000).You can download this Firewall with complete source code from the hyperlink provided at the bottom of the page.