Firewalls are a great way of stopping intrusion into your network and their are lots of solutions for it but sometimes it becomes essential for you to give extra layer of protection to your network other than relying on your router firewall. As we are getting more and more attached to the internet using mobiles/laptops/desktops or even playstation or other devices it is possible someone out their maybe easily able to hack inside your network and take control over your devices. A neat solution is to implement a robust firewall system which remains updated to the latest threats and give overall great protection for your network one of such distribution is IPCop which can provide good protection for free. It is a Linux firewall system and if you keep up to date it will provide you with the very best protection available. You can simply install it over some old lying desktop with 2 Network Inteface Cards (NIC). For detailed installation you can visit http://www.ipcop.org
Enjoy!