When compared to the rest of the computing industry, firewall technology is quite an adolescent. The pioneering generation of firewall architectures, called packet filter firewalls, first appeared around 1985 courtesy of the IOS software division of computer networks giant Cisco.
Three years later, the first paper on firewall technology came out, authored by Jeff Mogul of the Digital Equipment Corporation (DEC). However, during of all these years, Dave Presetto and Howard Trickey of AT&T Bell Laboratories were developing the second firewall generation - circuit level firewalls. Their work encompassed the decade, starting from 1980 and concluding in 1990.
In 1990 and 1991, Bill Cheswick, Marcus Ranum, and Gene Spafford published papers that described the third generation of firewalls, called application layer firewalls (or proxy-based firewalls). This triumvirate researched and developed the third generation independently of each other, with Ranum receiving the most attention for his work.
In 1991, the DEC released the first firewall commercial product, named "SEAL". SEAL was based on the work of Marcus Ranum. The following year, Bob Braden and Annette DeSchlon of the University of Southern California began to develop their own fourth generation packet filter firewall system, called "Visas". The system is the first one to have had a visual integration interface, replete with colors and icons. Visas formed the basis of the commercial product FireWall-1, released in 1994 by the Israeli company Check Point Software.
In 1996, Scott Wiegel of the Global Internet Software Group began work on the fifth generation of firewalls, called the Kernel Proxy architecture. A year later, Cisco released the first commercial product based on the Kernel Proxy technology, the Cisco Centri Firewall.
Recently, the industry has seen the convergence of firewall technologies and intrusion-prevention systems. This has led to some people calling the fusion the "Next Generation Firewalls".
