History of Firewalls
The Digital Equipment Corporation developed the first firewall in 1988. This was a simple packet-filter firewall. Packet-filter firewalls inspect data packets as they pass between source and destination. If a packet matches a security rule, then the firewall will drop the packet and send an error response to the source.
In the early 90s, Bell Labs invented the second generation of firewalls. These firewalls used stateful filters and were also called circuit-level gateways. They worked similarly to the first generation firewall but were an upgraded version. Firewalls with stateful filtering remember information about previous packets and use context for more security.
The third generation of firewall filtered internet traffic was used in the application layer. The first version was released in 1993 and called Firewall Toolkit (FWTK). These firewalls were user-friendly for the first time, allowing even non-technical people to set firewall rules. They also understood applications and protocols and could prevent threats that packet filtering let through like application targeted malicious data coming from a trusted source.
There have been many advances in firewall technology since. Most firewalls still use application layer analysis, but the techniques used for analysis have improved. Let’s look at the common types of modern firewalls next.