- A firewall is software or firmware that prevents unauthorized access to a network.
- It inspects incoming and outgoing traffic using a set of rules to identify and block threats.
- Firewall accept/reject/block Traffic with respect the assigned rules
- Firewalls are used in both personal and enterprise settings, and many devices come with one built-in, including Mac, Windows(Windows Defender), and Linux computers.
How It Works :
- Firewalls intercept network traffic at a computer’s entry point, known as a port.
- Firewalls perform this task by allowing or blocking specific data packets (units of communication transferred over a digital network) ,
- based on predefined security rules. Incoming traffic is allowed only through trusted IP addresses, or sources.
Classification Based on Usage Location :
- Host based firewalls : Firewalls Protects Individual Devices , Ex : Like PC(Windows Defender)
- Network Based : Protect It’s Connected Entire Network , Ex : Enterprise Local Area Network Firewall
Classification Based on Filtering Method :
| Firewall | Information | Example | |
| 1 | Packet Filter | When a packet passes through a packet-filtering firewall, its source and destination address, protocol and destination port number are checked. | At TCP Allowing SSH 22 Port |
| 2 | Stateful inspection | Examines network traffic to determine whether one packet is related to another packet. | Packet Comparing |
| 3 | Proxy (Application Firewall) | Inspects packets at the application layer of the Open Systems Interconnection (OSI) reference model. | Blocking malware or certain websites, |
| 4 | Next Generation FW – NGFW | Multilayered approach to integrate enterprise firewall capabilities with an intrusion prevention system (IPS) and application control. | Network Address Translation (NAT), Uniform Resource Locator (URL) blocking and virtual private networks (VPNs) |
Firewall Hardware + Firmware Device Manufacturers:
- Cisco Firewalls
- Barracuda firewalls