What is a Firewall?
Firewall is a piece of software or hardware that checks all incoming and outgoing communications on a network based on a set of security rules you or your administrator sets up. The firewall keeps out unauthorized traffic and lets in only communications that meet your security criteria, making it a crucial tool to keep cyberattackers at bay. Firewalls are available as software or in hardware form, and can be found on every Mac and Windows computer. Some are bundled with other cybersecurity programs, while others are purchased as standalone software or offered separately from hardware vendors and online stores.
Like a nightclub security guard, a firewall looks at each data packet to determine where it came from and where it’s going or both before waving it through the gate. If the data fails to pass security checks, it is rejected or dropped.
Most of the time, you’ll be working with TCP packets, which have unique sources and destinations to identify your PC on the Internet as well as ports, which help to identify what kind of applications a data packet is supposed to be used for. A good example is a web browser sending data to a web server over TCP with a port number of 80.
The concept of the firewall was developed by multiple people in the late 1980s and early 90s, including Reid, Mogul, and Vixie at Digital Equipment Corp (DEC). But it was primarily Reid’s work that led to the first true firewall product, released in 1991.