i dont know if i can call it a security tool but i am using it for quite some time now and i will recomend it to you all to place one at your home

explanation:

it is a firewall os based on linux that can run on a small pc with low specs
and i truely love it and it bloks more than every software firewall in the world


URL: http://www.smoothwall.org/

ow and i almost forgot it is one of the few i havend been able to break true^^

It's a great firewall. Just pull that old Pentium III with 256MB of RAM, add a couple of cheap NIC's and you're good to go!