1. Introduction to Linux Firewall touch@coe.psu.ac.th

2. TCP/IP TCP/IP Layers IP Headers TCP Headers UDP Headers ICMP Headers

3. TCP/IP Layers Application Layer Presentation Layer Session Layer Transport Layer Network Layer Datalink Layer Physical Layer

4. IP Header

5. TCP Header

6. TCP Connections

8. UDP Header

9. UDP Connections

10. ICMP Header

11. ICMP Echo Request/Reply

12. ICMP Connections

13. ICMP Destination Unreachable

14. ICMP Connections

15. What is IP Filter Mainly work on Layer 2 (Datalink) Able to work on Layer 3 (IP) Able to work on Layer 4 (TCP, UDP)

16. IP Filtering Term and Expression Drop/Deny Deny State Chain Table Match Target Jump Rule Accept Policy

17. How to Place IP filter Put the firewall between the network you would like to control network traffic DMZ is a good idea to have Two common policy Drop everything Allow everything

18. Tables and Chains in iptables Default Table INPUT FORWARD OUTPUT

19. Tables and Chains in iptables nat PREROUTING POSTROUTING OUTPUT

20. Tables and Chains in iptables mangle INPUT PREROUTING POSTROUTING OUTPUT

21. Packet Traversal through Tables

22. Basic of iptables command iptables [-t table ] command [match] [target/jump] command -A, --append iptables -A INPUT... -D, --delete iptables -D INPUT --dport 80 -j DROP, iptables -D INPUT 1 -R, --replace iptables -R INPUT 1 -s 192.168.0.1 -j DROP -I, --insert iptables -I INPUT -s 192.168.0.10 -j DROP

23. Basic of iptables command iptables [-t table ] command [match] [target/jump] command -F, --flush iptables -F -L, --list iptables -L -P, --policy iptables -P INPUT DROP

24. iptables command options -v, --verbose -n, --numeric

25. Generic Matches -p, --protocol -s, --src, --source -d, --dst, --destination -i, --in-interface -o, --out-interface --sport, --source-port --dport, --destination-port --syn --icmp-type