• Firewall (packet filter)
• Default rules
• Hardware vs. Software
• Stateful vs. Stateless

• Know the basic rules for setting up a firewall
• Configure a basic IPtables firewall
• Understand the difference between a stateful/stateless firewall

Commands:
iptables
iptables -t filter -L -nv | less
/proc
levy.pl (--log-level info)
/sbin/iptables -A DUMP -p tcp --dport 137:139 -j DROP
/sbin/iptables -A DUMP -p udp --dport 137:139 -j DROP
nmap and nmapfe
nmap -vv -sS -p 1-65535 -T insane -O -P0 140.198.x.x ip_conntrack_ftp
iptables-save
then copy that to /etc/sysconfig/iptables for redhat's setup
Assuming you have rpmforge as a repository, do the following:
yum install nmap-frontend
zenmap

• What is a stateful firewall? How is it better/worse than a stateless one?
• What type of firewall would be best for ftpd?
• What are the limitations of firewalls? Why would adding snort in addition to a firewall be a good idea?
• What should the default rules be on a firewall for INPUT, OUTPUT and FORWARD? (With iptables, using stateful rules, is that still considered an issue?)
• Why will you get a different result if you scan your system's firewall from the inside vs. the "outside"?
• What is NAT? How about VPN?

• Make an iptables script (use firestarter if you wish)
• Then turn off portsentry
• Go to GRC.com and try both "Shields up" and Probe my Ports
• (WAIT! DON'T DO this yet!)Go to Hacker Whacker click on "Free Security Scan" and give them an email you can access easily and scan yourself (I want a copy of the results).
  DON'T do this unless you have portsentry off, your firewall configured and all your updates in place.
• Scan Each Other
  1. Person scanning must turn firewall off
  2. Person BEING scanned must kill portsentry
  3. Person scanning types "zenmap" as root
  4. Person scanning checks ports 1-65535
  5. Person Scanning puts in the other persons IP#
  6. Person Scanning then copies results to a file and prints them for the teacher.
  7. You then reverse roles (ie turn firewall back on while other turns it off, same for portsentry)

• IPtables Tutorial
• Netfilter home of iptables
• Levy a perl script to generate basic iptables rules
• IPcop
• Firestarter
• Firewall Tools at Sourceforge
• The Wilde Netfilter excellent article from Linux Journal
• IPTables Tutorial
• Example firewall script
• Firewall script from IPTables Tutorial