If you want your Linux-Box to have a firewall, you must first ensure that your kernel has been compiled with the relevant options turned on. How to configure your kernel, with enabling the options to be either compiled into the kernel or as modules, depends on your personal preferences and experience. Note, that for the quoted scripts it is assumed that the modules need to be loaded at first. Network options menu Network packet filtering: Y Unix domain sockets: Y or M TCP/IP networking: Y IP: advanced router: Y IP: verbose route monitoring: Y IP: TCP Explicit Congestion Notification support: Y IP: TCP syncookie support: Y IP: Netfilter Configuration menu Every option except: Y or M ipchains (2.2-style) support N ipfwadm (2.0-style) support N Fast switching: N