What Is a Firewall?
Firewalls are a key component of network security, preventing attacks and keeping your data safe. They work like a border guard, inspecting and comparing incoming packets with a set of preconfigured rules before allowing them to enter your system. Firewalls are available in hardware or software and can be installed on a single device, on the whole network, or both.
The term “firewall” is a reference to the physical walls used to contain fires. Network firewalls are designed to contain online threats and prevent sensitive information from being exposed to unauthorized users or malicious software.
There are many different types of firewalls, both in hardware and software, but they all share the same basic functionality. These firewalls monitor and control the inbound and outbound network traffic for the device on which they are installed. We can install these firewalls in devices as third-party software or we can buy them as hardware products. In addition, many operating systems include a built-in firewall feature that can be enabled for added protection.
Typically, these firewalls offer a simple filtering at the lowest level of the OSI networking stack that only checks individual IP packets for source and destination addresses, port numbers and the protocol type code (UDP and ICMP). They are also referred to as packet-filtering or network layer firewalls.
Some firewalls offer more in-depth inspection at the application layer of the OSI network stack, comparing data traits such as usernames, passwords and encryption, to prevent unwanted applications and malware from entering the network. They are also referred to as application layer firewalls.