Firewalls are arguably the “granddaddy” technology of the current IT security world. In the late 1980s, the earliest firewalls were little more than filtering rule sets on routers. As more organizations connected to the Internet in the early to mid-90s, the demand for firewalls evolved and companies like DEC, Raptor and TIS introduced commercial products. These early firewalls monitored connections for what were, at the time, the most popular application-layer protocols: FTP, Gopher, SMTP (email), and Telnet.

Around the mid-90s, something  interesting happened to the firewall market. A massive debate erupted around which technology implementation was more secure for network perimeter firewalls: Stateful protocol filtering (sometimes referred to a