What is a Firewall?
You have probably heard the term firewall before or have seen it in action yourself. If you have ever tried to access a social media site while on a school’s network and were blocked, that is the firewall blocking you from accessing the site. This blog post will explain how firewalls work and the different types of them.
Simplified Explanation of a Firewall
Think of a firewall like your network's security guard. It is a software or hardware solution that monitors network traffic based on security rules set by a network administrator. A firewall only lets data that meets certain criteria through and blocks data that does not.
How Firewalls Work
The overall goal of a firewall is to prevent malicious traffic like viruses and hackers that can be harmful to your computer. Data sent over a network is usually checked by an access control list (ACL) which is a set of rules that determines which traffic is allowed or blocked. ACLs are configure to block traffic through different customizable aspects. If data passes the criteria of the ACL, they will get passed the firewall and sent to their destination.
How are firewalls customizable?
You can add or remove filters based on many conditions that deem traffic good or bad on a network. Keep in mind that one's firewall can be completely different than another's based on what that certain organizations allows.
These conditions include:
IP Addresses
Domain Names
Protocols
Ports
Specific/explicit words and phrases
Types of Firewalls
Firewalls can be either be physical hardware that is a piece of equipment installed or a software program installed on each computer on a network that guards the network by regulating traffic through port numbers and applications.
Firewalls can use the following methods to control the traffic flow of the network:
1. Packet Filtering Firewalls
This is the most common type of firewalls since it examines network packets and prevents "bad" ones from passing through the network if they do not meet the security protocols requirements that are established by an organization/admin. Network packets are simply small pieces of data sent over a network.
2. Proxy Service
In general, a proxy is a method of doing something on somebody else's behalf. Therefore, a proxy service in this case is a specialized application or server program that takes information from the internet that is retrieved by the firewall and examines the data to see if they are OK or not to pass through the network.
Ex) An organization does not want you accessing your personal email on company time, so they configure the proxy server to deny access to specific email sites and you are left with a message that you are blocked from that site by your administrator.
3. Stateful
A stateful firewall is a network based firewall that completely monitors active network connections by analyzing traffic and data travelling through the network. This method provides a better understand of the traffic flow of the network because it understands the overall pattern of incoming data and once the data is approed by a stateful firewall, it is added to a kind of safe list that lets the it travel with less restrictions. Think of it as going through an airport and if you do not carry any suspicious objects on you, you can go through the airport freely and reach your destination. If you do carry something suspicious, you will be blocked and it will be a lot harder for you to get to your destination.
4. Stateless
A stateless firewall is not as involved in the network's traffic activity like a stateful firewall is since it does not track the overall pattern of data but instead uses clues from the data like the destination address and source and then allows or blocks it based on the rules enforced.
So, the next time you try to access an application or website on your device, think of how firewalls are working!
Thank you for reading! Share this post with your friends and family and stay tuned for more simplified technology explanations.