Once they were border controls, then customs and excise, now they are the police, the fire brigade and the health service. Can the firewall become the sole security device in the enterprise? Zaphod Beeblebrox, the two-headed anti-hero of Douglas Adams’ Hitchhiker’s guide to the galaxy, wears the future of firewalls on his head. His Joo Janta 200 Super-Chromatic Peril Sensitive Sunglasses turn black at the first hint of danger. This saves him from witnessing frightening events, so he remains cool and un-panicked in a dangerous universe.

To understand how such advanced content filtering might come from the evolution of the firewall, it is useful to recap how we got to where we are today.