Network Firewalls: their Classification and Functions
Firewalls are essential security solutions for networks, safeguarding computers and devices connected to them. They act as barriers, controlling and monitoring the amount of incoming or outgoing traffic of a network, with data coming in the form of packets (small units of data).
A Host-Based Firewall is installed on individual devices like laptops, servers, or mobile phones and protects only that one system. On the other hand, a Network Firewall safeguards a whole network, usually placed at the entry/exit point between your internal systems and the internet.
Network Firewalls can be implemented as either hardware or software. The main types include Packet Filtering Firewall, Stateful Inspection Firewall, Proxy Firewall (Application Level), Circuit-Level Gateway, Web Application Firewall (WAF), and Next-Generation Firewall (NGFW).
Packet Filtering Firewall checks packet headers and decides whether to allow or block them. Stateful Inspection Firewall monitors active connections and makes decisions based on the context of traffic. Proxy Firewall acts as a middleman between user and destination and filters dangerous content. Circuit-Level Gateway validates if a connection is successfully established but doesn't inspect actual data. Web Application Firewall specifically protects websites and web apps from attacks like SQL injection or cross-site scripting. Next-Generation Firewall combines traditional firewalls with modern features like app control, intrusion prevention, malware detection, and encrypted traffic inspection.
Hardware Firewall is a physical box or appliance that connects to a network, often used in large or office environments, resembling a security gate at the main entrance. Software Firewall is installed as a program on a device or server, easier to set up and ideal for individuals or virtual setups, like installing a firewall app on a laptop.
A Perimeter Firewall is placed at the edge of a network, filtering traffic coming in and out from the internet, acting like a fence with a gate that controls who gets into a property. An Internal Firewall is placed between different segments inside a network, such as departments or sensitive zones, with access rules similar to department doors. Distributed Firewall applies security rules at multiple endpoints across the network, rather than just at the main entry/exit point.
While firewalls offer significant benefits, they do have limitations. Cost can be a factor, as some types (like hardware firewalls) can be expensive. They can also restrict users, slow down operations, and require continuous updates and maintenance.
The company that developed the first Next-Generation Firewall (NGFW) is Palo Alto Networks, and their NGFW was first introduced in 2007.
In summary, firewalls play a crucial role in network security, offering various types and functionalities to protect individual devices and entire networks from unauthorised access and malicious activities.
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