Firewall technology evolution
Fundamental firewall technology has not changed much in recent times. It separates into a few broad categories and most vendors incorporate some or all of them into their toolset.
The most common baseline requirement these days is Stateful Packet Inspection (SPI). Vendors also generally incorporate forms of individual packet filtering as well as port filtering. There are two other features now commonly found in most mainstream firewalls these are; that they act as application gateways or proxies, and can also have rule/policy-based access control lists-referencing IP addresses/ranges, network user-IDs etc. Some vendors also enable the administrator of the device to set up advanced rule sets to enforce the enterprise's security policies and framework, be it content filtering, Web access/content control, blacklists/whitelists, or even bandwidth shaping and management.
Virtual firewalls and virtual policies/rule-sets are now making an appearance -- allowing several administrators to have access to their own areas and rules on the one appliance.