What is a Firewall?
A firewall keeps harmful data from entering your agency’s computer systems, protecting against backdoors, macros, remote logins, malware, viruses, denial-of-service attacks, and spam. Your hardware or software based firewall uses a series of rules (also known as policies) to evaluate each data packet, letting through those that meet certain criteria and discarding those that fail. Your administrator updates these rules regularly to address evolving threats and keep your agency’s cybersecurity robust.
Firewalls work at the network level, evaluating the data transfer protocol rather than the packet header. This type of firewall looks at the whole request for a connection, determining where it came from, where it is going, and which ports are used in both cases. If the request is valid and functional, the firewall will permit an ongoing open connection between networks. This can be dangerous because malicious actors could use a valid request to enter the agency’s system and continue to steal information or access devices over time without interruption.
Various staff at AT&T Bell Labs worked on the first modern firewall technology in the late 1980s and early 1990s. In 1989, Presotto, Sharma, and Nigam developed the circuit-level gateway firewall which allowed ongoing connections instead of reauthorizing them for each individual data packet. In 1991, Ranum introduced security proxies at DEC, building on the circuit-level gateway work. These developments made firewalls easier to deploy and use, contributing to their rapid adoption. This is why many businesses and homes have firewalls today.