1. Firewall Techniques
Matt Cupp

2. Overview What is a firewall? Several firewall techniques
Popular firewalls
Advantages vs Disadvantages

3. Firewalls What is a firewall? Software or Hardware
A system to prevent unauthorized access to a private network
Software or Hardware
Application-Level or Network-Level

4. Techniques
Packet Filtering
Network Address Translation
Proxy Server

5. Packet Filtering Inspects each packet entering or leaving the network
Accepts or rejects based on user-defined rules
Can be transparent to the user, but also quite difficult to configure
Susceptible to IP Spoofing
Editing the packet headers to that of a trusted IP address to gain access to target system

6. Network Address Translation
The firewall or router rewrites the source and destination of IP packets as they pass through the gateway
This allows multiple hosts in a network to access the internet using a single IP address
Helps with load balancing
Redirects connections pointed at a server to other randomly selected servers

7. Proxy Server Uses combinations of various techniques
Server that acts as a gateway between trusted networks and untrusted networks
Requests between the two areas are intercepted by the proxy server and inspected to see if the request will be allowed or not
The true network addresses are hidden by the proxy server

8. Proxy Server Disadvantages Expensive to set up and maintain
If the server is setup incorrectly, the gateway could be compromised or shut down

9. Firewall Examples Windows XP Firewall Various Cisco products
Hardware
Linux iptables
Check Point VPN-1
Highly Reccommended

10. Advantages vs Disadvantages
Extensive Firewall protection will ensure that your system is safe
Good practices will ensure you can identify an attacker
Disadvantages
More protection = Less Performance

11. References http://geodsoft.com/book/security/techniques.htm