firewall

Pluralfirewalls

Formsfirewalls, firewalling, firewalled

1. 1
   nouncountable

   Software that monitors traffic entering and leaving a private network or personal computer, allowing or blocking it based on its perceived threat.

   Like a customs checkpoint that inspects everything crossing a border and stops whatever looks like a threat.

   The company installed a firewall to keep intruders out of its internal network.

   When the firewall flagged the incoming packets, the administrator reviewed the logs.

   Note

   In practice the term covers dedicated hardware as well as software: whatever inspects traffic against a set of rules and enforces a boundary between a trusted network and an untrusted one. The idea of a wall that holds danger back is carried over from the building trade. The verbs to protect with one and to block with one grew from this noun.

2. 2
   nouncountable

   A fireproof barrier that prevents the spread of fire between or through buildings, vehicles, or aircraft.

   Like the sealed bulkhead on a ship that stops flooding in one compartment from reaching the rest.

   The firewall in the engine compartment shields the cabin from heat and flames.

   Each townhouse is separated from the next by a firewall rated for two hours.

   Similarbulkhead

   Note

   A plain compound of fire and wall, and its neighbors build the word the same way: Dutch brandmuur, German Brandmauer, Swedish brandvägg, Icelandic eldvegg. The wall need not stand between buildings. It also separates electrical substation transformers, and in a car or aircraft it is the partition between engine and cabin. The protective image here is the one the computing senses later borrowed.

3. 3
   verbtransitive

   To protect a computer or network by installing and configuring a firewall.

   Like hiring a doorkeeper who screens everyone before letting them into the building.

   The administrator firewalled the entire subnet to limit outside access.

   They firewall every new server before it goes live.

   Similarsecure, protect, shield

   Note

   Here the object of the verb is the thing kept safe behind the wall: you firewall a server, a subnet, a whole network. The verb takes regular endings, so its forms are firewalls, firewalling and firewalled, with no change to the stem.

4. 4
   verbtransitive

   To block specific traffic, an address, or a connection by means of a firewall.

   Like a bouncer turning away specific troublemakers at the entrance while letting others pass.

   The IT department firewalled the malicious IP range within minutes.

   Network admins firewall any port that isn't actively in use.

   Similarblock, blacklist, filter

   Oppositeunblock, allow

   Note

   The same transitive verb turned around: the object is now what gets shut out, such as an IP range, a port or a connection. Only the object tells it apart from the protecting sense. Firewalling a server shields it, while firewalling an address bars it, so in writing it pays to make clear which side of the wall the object stands on.

5. 5
   verbslangintransitive

   To run an engine or vehicle at maximum power or acceleration.

   Like flooring the gas pedal until it can't go any further.

   Racers firewall through the final lap, engines screaming.

   He firewalled as soon as the track straightened out.

   Similaraccelerate

   Oppositebrake, decelerate

   Note

   Slang from cockpits and race cars. It describes shoving the throttle all the way forward, toward the barrier between engine and cabin. The verb usually stands without an object (racers firewall down the straight). It belongs to the talk of drivers and pilots rather than to technical or formal writing.

6. 6
   nouncountable

   A hypothetical region of high-energy quanta that an observer falling into a black hole would encounter at or near the event horizon.

   Like discovering a blazing barrier exactly where you expected an invisible, harmless threshold.

   Whether a firewall forms at the event horizon remains a matter of theoretical debate.

   A firewall would violate the equivalence principle by making the horizon a special place.

   Note

   A physicist's conjecture rather than an observed object, so it is usually discussed in the conditional: a firewall would form, an observer would meet it. It was proposed to resolve the black-hole information paradox. Its cost is a clash with general relativity, which predicts that an infalling observer should cross the horizon smoothly and find nothing special there.

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