Firewall defined

The term ‘firewall’ originally referred to a structure that is supposed to confine fire within a closed space, thus hampering its spread and mitigating its harmful effects on humans and property.

By analogy, in network security a firewall monitors incoming and outgoing traffic and simply blocks out harmful or potentially unwanted content and communication. Working as a gatekeeper between trusted and untrusted networks, a firewall ensures legitimate content is able to pass through while blocking out potential hackers threatening to misuse or corrupt your device.

What is the purpose of a firewall?

The biggest benefit for users is enhanced security. By using a cybersecurity firewall you set up a security perimeter that can help to protect your computer or network from harmful incoming traffic.

This technology can also filter harmful outgoing traffic. By doing this, firewalls lower the chance of undetected data exfiltration by a malicious insider, as well as reducing the risk that the devices behind the firewall will become a part of a botnet – a large group of internet-connected devices enslaved by the attackers for malevolent purposes.

What is the purpose of a firewall?

The biggest benefit for users is enhanced security. By using a firewall you set up a security perimeter that can help to protect your computer or network from harmful incoming traffic.

This technology can also filter harmful outgoing traffic. By doing this, firewalls lower the chance of undetected data exfiltration by a malicious insider, as well as reducing the risk that the devices behind the firewall will become a part of a botnet – a large group of internet-connected devices enslaved by the attackers for malevolent purposes.

Why is a firewall important?

With many changes in both the work and home environment, how much people exist online, and what data they’re storing and accessing regularly through the internet, a firewall is more important than ever. Alongside this steady increase in cyberthreats, there are a number of reasons why a firewall is so important.

Remote working

With so many users and companies making the switch to remote or hybrid working, there’s also an increase in threat level. Whether people are performing remote logins, accessing sensitive files at home or simply just being online more often on a less secure network, remote working can put them at a greater risk. A cybersecurity firewall is essential for both work and personal devices.

Personal data

The sheer amount of personal and sensitive data that is now being stored online makes a firewall incredibly important. Protecting your login details is just the beginning. If you’re not careful, you could expose everything from your name and address through to banking details, your national insurance number or even details on your mortgage. Identity theft is as big a risk as simple theft.

Business data

It’s not just individuals’ data that needs protecting. Many businesses are seeing an increase in employees accessing sensitive information from increasingly less secure locations. When everything was centralised, it was easier to invest in security features for your network. Now, there’s no guarantee where employees are accessing the work system from, and also a number of more inventive ways for cybercriminals to try and steal it.

How does a firewall work?

There are multiple types of firewalls, each using a different approach to traffic filtering. First generation firewalls worked as packet filters, comparing basic information such as original source and destination of the packet, the port being used, or the protocol against a predefined list of rules.

Second generation comprised the so-called ‘stateful’ firewalls, which added another parameter to the filter setup, namely connection state. Based on this information, the technology could determine if the packet was starting the connection, was a part of an existing connection, or wasn’t involved at all.

Third generation firewalls were built to filter information across all layers of the OSI model – including the application layer – allowing them to recognise and understand applications as well as some of the widely-used protocols such as File Transfer Protocol (FTP) and Hypertext Transfer Protocol (HTTP). Based on this information, the firewall can detect attacks trying to circumvent it via an allowed port or misuse of a protocol.

The latest firewalls still belong to the third generation, however they are often described as ‘next-generation’ (or NGFW). They combine all the previously used approaches with deeper inspection of the filtered content, e.g. matching it against a detection database to identify potentially harmful traffic.

These modern firewalls often come with additional security systems built into them such as virtual private networks (VPN), intrusion prevention and detection systems (IPS/IDS), identity management, application control and web-filtering.

 

Third generation firewalls were built to filter information across all layers of the OSI model – including the application layer – allowing them to recognise and understand applications as well as some of the widely-used protocols such as File Transfer Protocol (FTP) and Hypertext Transfer Protocol (HTTP). Based on this information, the firewall can detect attacks trying to circumvent it via an allowed port or misuse of a protocol.

The latest firewalls still belong to the third generation, however they are often described as ‘next-generation’ (or NGFW). They combine all the previously used approaches with deeper inspection of the filtered content, e.g. matching it against a detection database to identify potentially harmful traffic.

The different types of firewall

The first commercial firewalls designed for computer networks were developed in the late 1980s by Digital Equipment Corporation (DEC). The technology gained prominence and became widespread over the following decade due to the rapid growth of the internet worldwide.

Since then, there have been a number of new types cybersecurity of firewalls introduced, all designed to protect you in different ways. There are two different ways to categorise a firewall. The first is based on what they protect; these firewalls are either ‘network’ or ‘host-based’. One of these protects entire networks, whereas the other usually protects individual devices or computers.

Virtual firewalls & cloud-based firewalls

A virtual or cloud-based firewall is another way firewalls can be applied to a network. They are used when a hardware firewall is difficult to implement. Software firewalls and virtual firewalls can do the same things as other firewalls, but they aren’t limited to hardware. They can be used to protect cloud based networks and software defined networks (SDN).

Understanding firewalls for home and small office use

A firewall is essential for any private network connecting to the internet. In a small office environment, this could be as simple as a handful of computers, a server, your printer and a few other connected devices like phones and tablets.

Protecting your data at device level can be a very good idea, but when you’re setting up a network it’s also important to have network-level security. This is essential for a small office and should be implemented immediately.

Do you need a firewall at home?

The same can be said for home networks. On a home network, you may have a multitude of devices connecting to the internet at any one time. This includes your laptops, smart TVs, smartphones, tablets, consoles, printers, your home security system and potentially even your fridge. Your network is only as secure as its weakest link, so having a firewall that protects your whole network is incredibly important.

For home protection, it’s always advisable to employ antivirus software and other security software in additional to your firewall. It’s also strongly recommended that you keep all your devices updated to their most recent software version. If you’re worried, ESET offers a free online scanner you can use. You should also secure your wireless router.

What threats do firewalls protect against?

Firewalls protect against a variety of different security threats by controlling the network traffic coming into and going out of a network. The key threats firewalls can prevent include; malware, viruses, phishing or spoofing attacks, hackers and unauthorised data exporting.

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Protect your company endpoints, business data and users with ESET's multilayered technology.