Firewall Basics: Understanding Network Security

This tutorial provides a complete overview of networking basics, covering essential concepts such as circuit switching vs. packet switching, TCP/IP protocol fields, ARP/RARP protocol fields, IP addresses, MAC addresses, and various networking devices. We’ll explore hubs, switches, bridges, routers, gateways, and, of course, firewalls in detail.

Topics Covered:

• Circuit Switching vs. Packet Switching
• LAN vs. WAN vs. MAN
• What is an IP Address?
• What is a MAC Address?
• Basics of OSI and TCP/IP Layers
• What is a Hub?
• What is a Switch?
• What is a Bridge?
• What is a Router?
• What is a Gateway?
• Firewall Basics
• TCP/IP Packet Format
• ARP Protocol Format

What is a Firewall?

A firewall is a hardware and/or software system that inspects all incoming and outgoing network packets from a system or LAN connected to the internet. Its primary purpose is to prevent unauthorized connections and protect against spam or viruses that could affect the system or LAN.

Types of Firewalls

Several types of firewalls exist, each employing different methods to secure your network. A firewall can utilize one or more of these techniques:

• Packet Filter: This type examines each individual packet as it enters or leaves the network. This process is called IP spoofing.

• Application Gateway: Operating at the application layer, this firewall is tailored for specific applications like FTP and Telnet-based client-server setups.

• Circuit Level Gateway: This type becomes active when a TCP or UDP connection is being established. Once the connection is established, it doesn’t perform further checks on the packets exchanged between systems.

• Proxy Server: This firewall scrutinizes all packets/messages entering and exiting the LAN/network. Its effectiveness lies in hiding the original/actual IP-based network addresses, enhancing security and privacy.

Many firewalls combine two or more of these techniques for enhanced protection.

Firewall Software

The following are popular firewall software options that can help protect your system from unauthorized access and attacks:

1. COMODO Firewall
2. PC Tools Firewall Plus
3. ZoneAlarm Firewall
4. Ashampoo FireWall
5. Online Armor
6. Agnitum Outpost Firewall
7. Filseclab Personal Firewall Professional Edition
8. Sygate® Personal Firewall PRO
9. Symantec Norton Personal Firewall 2004
10. McAfee Personal Firewall Plus

Firewall Hardware Manufacturers

Here are some of the leading manufacturers of firewall hardware devices:

1. Cisco
2. ZyXEL
3. NETGEAR
4. DELL
5. WatchGuard