A firewall is a protective barrier that controls what can pass through, either as a physical wall that stops fire from spreading in a building or as software that guards a computer network from unwanted access.
It began as a literal “wall against fire” in buildings and ships. Later, the term was borrowed into computing to describe a digital barrier that blocks harmful traffic.
The internet “firewall” is a metaphor built from real bricks: both aim to stop a dangerous blaze from reaching what’s valuable. The image is so strong that we also talk about “firewalls” in business and politics to block conflicts of interest.
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