In computing and networks, a firewall is software, hardware or firmware (which is permanent software programmed into a read-only memory.) that follows a specific set of rules to decide whether to allow information or data to enter or leave a network.
Firewalls have been a crucial defence in network security for over 25 years. They are a virtual barrier between sources that are checked and trusted, and untrusted sources that come from outside an internal network.
Firewalls can be used for a wide range of devices and systems to lower the risk of malicious data travelling to and from the device.
The term firewall is a metaphor relating to a wall or partition designed to inhibit or prevent the spread of fire. The most common ones you see are fire doors in a commercial building or school. There are two main types of computing firewall; network based and host based.
Host-based means it’s installed on individual servers and monitors signals going in and out. A network-based firewall is held in the cloud as a virtual firewall.
When you’re looking at firewalls, you’ll come across some various terms within those host and network-based firewalls, proxy, stateful inspection, unified threat management (UTM), next-generation firewall (NGFW) and Threat focussed NGFW.
Why do you need a firewall?
Firewalls are just the first line in the defence against hacks and malicious intent.
In the same way that you lock your doors and windows before leaving the house, your firewall locks out unwanted intruders and makes you much less vulnerable to hackers who want to access your data or imitate your company (also known as spoofing).
Some of the most common attacks are IP spoofing, network packet sniffers, man-in-the-middle attacks, distribution of sensitive internal information to external sources and password attacks.
Password attacks can be achieved via password guessing (like you see in the movies), brute force login (where a programme guesses at a much higher rate per second but can often crash a system due to the resources required to cope with the constant attack) and password cracking (where the attacker gains access to the file on a computer that stores your passwords).
The results of not having adequate firewall protection can be minor or devastating. Sometimes the downtime alone is the most costly part of the disruption, but other outcomes can be damage to a company’s reputation or loss of crucial information.