What Is Firewall?

Written by John Harris, Updated on October 10, 2023

What Is Firewall?

A firewall is a security system, either hardware or software-based, that is designed to protect a private network (such as a computer or a network of devices) from unauthorized access while allowing authorized communication to pass through.

It acts as a barrier between the internal network and the external network (usually the Internet) and monitors all incoming and outgoing network traffic.

Why Do You Need Firewall?

Firewalls, especially the advanced ones like Next Generation Firewalls, work to stop harmful software and attacks on applications. They quickly detect and fight intrusions across the whole network, thanks to features like integrated intrusion prevention systems. By using a firewall, you can set rules to allow or block traffic, adding an extra layer of security to your network.

Types of Firewalls

There are several types of firewalls, each with its own approach to filtering and controlling network traffic.

Packet Filtering Firewall:

  • Examines packets of data based on predefined rules (such as IP address, port numbers, protocols) and allows or denies them accordingly.
  • Filters packets at the OSI model's network layer (Layer 3).

Stateful Inspection Firewall:

  • Keeps track of the state and context of active connections, making decisions based on the context of the traffic rather than individual packets.
  • Provides a higher level of security by understanding the state of the communication (e.g., whether it's part of an established connection).

Proxy Firewall (Application-Level Gateway):

  • Acts as an intermediary between internal and external systems, intercepting all communication between the two.
  • Inspects and filters traffic at the OSI model's application layer (Layer 7).
  • Provides better security and anonymity but may introduce performance overhead.

Circuit-Level Gateway:

  • Works at the session layer (Layer 5) of the OSI model.
  • Establishes a circuit-level connection before allowing data packets to pass through.
  • Monitors the validity of sessions but doesn't inspect the contents of the packets.

Next-Generation Firewall (NGFW):

  • Integrates traditional firewall features with additional functionalities like intrusion prevention, SSL and SSH inspection, deep packet inspection, application awareness, and more.
  • Uses advanced techniques to identify and control applications, users, and content.

Application-Aware Firewall:

  • Analyzes the data packets to identify the specific application generating the traffic.
  • Controls access and policies based on the identified application.

Virtual Private Network (VPN) Firewall:

  • Secures communication over a public network (usually the internet) by encrypting and tunneling the data packets through a secure VPN connection.
  • Enhances security for remote users or branch offices connecting to the main network.

Advantages and Disadvantages of Firewall

Advantages Disadvantages
Cost is inexpensive It takes more time to get its traffic onto a particular network
Secure your system from intruders Can degrade your system’s performance
Can even protect multiple systems simultaneously Some firewalls do not find viruses, worms, Trojans, etc

Future of Firewall

The future of firewalls is expected to evolve in response to advancements in technology, cybersecurity threats, and changes in the way we use and access data, making it easier to deploy.

Integration of Artificial Intelligence (AI) and Machine Learning (ML):
AI and ML will likely be integrated into firewalls to enhance threat detection, automate response mechanisms, and improve overall security.

Zero Trust Architecture:
The Zero Trust model assumes that threats can exist outside and inside the network. Future firewalls will likely adopt this approach, emphasizing continuous verification and authentication of users and devices, regardless of location.

5G Network Security:
The rollout of 5G networks will require firewalls to adapt and secure higher speeds and increased connectivity, addressing potential vulnerabilities and risks associated with this technology.

Secure Access Service Edge (SASE):
SASE combines network security functions with WAN capabilities to support organizations' dynamic, secure access needs. Future firewalls will likely align with the SASE framework, integrating security with network capabilities.

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