A firewall is a network security system that is made in order to prevent and avoid unauthorized access to or from a private network.[1] It is a type of software that enables the enforcement of a set of rules about the various kinds of data that will be filtered and be allowed to enter or leave a network. A firewall can be implemented as either a software utility or as a hardware device, and even as a combination of both as long as it filters the data. This firewall just typically establishes a barrier between a trusted internal network and untrusted external network like the internet.

Furthermore, these are tools that will be used in enhancing the security and safety of all computer devices connected to a certain network such as the local area network (LAN) or the internet. They are considered as an integral part in order to have comprehensive security and safety in the framework for the network. A firewall is incorporated into a wide variety of networked devices to filter traffic and lower the risks that malicious packets traversing over public internet can affect the security of a private network.[2] In a nutshell, a firewall typically defends resources, validates access, manages and control network traffic, records, and reports on events and acts as an intermediary.


The main job of a firewall is to keep destructive forces away from your devices. Its task is similar to an actual firewall that keeps a fire from spreading from one place to another place. If there is an incoming packet of information that is flagged by the filters, then it is not allowed to go through. This is because when there is a packet passing through a packet-filtering wall, all the sources and destination addresses, protocol, and destination port number is being checked.


The following are the different types of firewalls and their functions:

Proxy-based firewall

It acts as a gateway between the end users who request the data and the source of data. All host devices connecting to the proxy will have a separate connection to the source of data. This firewall can filter them to enforce policies and mask the location of the recipient’s device and also protect the recipient’s device and network.

Stateful firewall

This firewall keeps track of a realm of information about connections and makes it unnecessary for the firewall to inspect every packet. With this, it reduces the delay introduced by the firewall. A stateful firewall simply examines the network traffic in order to determine whether one packet is related to another packet.

Web application firewalls

It protects the servers that support web applications and the internet from specific HTML attacks such as cross-site scripting, SQL injections, and others. This determines whether each client trying to reach the server should be given access.

Next generation firewalls

This type of firewall incorporates the rules for what individual applications and users are only allowed to do. It blends in data which is gathered from other technologies in order to make better-informed decisions about what traffic to allow and what traffic to drop. Next generation firewall also works by filtering network and internet traffic based on the applications or traffic types using the specific ports.

These types of firewalls have developed over the years, becoming progressive, and they take more parameters in considering whether traffic should be allowed to pass or not.[3]

Hardware and Software

Software firewall

This is designed in order to protect computer devices by blocking certain programs from sending and receiving information from a local network or from the internet. It is installed in computer devices like any other software programs which can be customized.

Hardware firewall

This firewall is found to all network routers which can be figured by the router setup screen. A hardware firewall is typically found in broadband routers.[4]

Firewall Techniques

The following are several types of firewall techniques:

Packet filter

The job of this technique is to look at every packet that enters and leaves the network and then accepts or rejects it based on the rules. This is considered as effective and more transparent to users than the others but difficult to configure.

Application gateway

It uses and applies security mechanisms to specific applications. This is also very effective but this imposes performance degradation.

Circuit-level gateway

It also applies security mechanism if the TCP or UDP connection is already established. If the connection has been made already, the packets can flow between the hosts without checking further.

Proxy server

This technique intercepts all the messages that enter and leave the network. It hides the true network addresses.

In real life, there are many firewalls that use two or more of these techniques.

A firewall has contributed a lot to the lives of the people especially in terms of privacy. It makes life not only of the computer devices but also of the people to be safe and secured. Through this, it helps block malicious programs because it prevents potential malware, viruses, and Trojan horses from infecting the system. Moreover, through a firewall, there will be fewer hackers which can cause loss of data and damage to computer devices.


The term firewall was used in the late 1980s to network technology which emerged at the time when the internet was fairly new in terms of global use and connectivity. The term referred to a wall that was intended to confine a fire within a building. The predecessors to firewalls for network security were the routers used in the late 1980s.

Common Issues and Solutions

The common issue that most of the people experience is that they are vulnerable to invasion of privacy every time they are online with a high-speed internet connection. These are the following situations that a person must be aware of and a situation when a personal firewall is important:

  • Surfing the internet at home by using "always on" broadband connection
  • Connecting to the internet through a public Wi-Fi network
  • Run a home network that needs to be kept isolated from the internet

With all of these situations, a personal firewall is highly configurable so that a person can easily create security policies that suit according to individual needs.[5]

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