Firewall policies , rulesets, straetegy ,chains, iptables

https://www.frozentux.net/iptables-tutorial/iptables-tutorial.html


http://www.tldp.org/HOWTO/Security-Quickstart-HOWTO/firewalls.html

nmap
http://insecurety.net/?p=42

http://www.networkuptime.com/nmap/page06-03.shtml