What Is a Computer 'Firewall'?

Defend your computer against hackers, viruses and more

Man using laptop
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Definition: A computer 'firewall' is an over-arching term to describe specialized defense systems for a computer network or a single computing device. The firewall term comes from construction, where specialized fire-prevention systems involve fire-resistant walls being placed strategically in buildings slow the spread of a fire. In automobiles, a firewall is the metal barrier between the engine and the front of the driver/passenger that protects the occupants in case the engine ignites.

In the case of computers, the firewall term describes any hardware or software that blocks viruses and hackers, and slows the invasion of a computer system .

A computer firewall itself can take hundreds of different forms. It can be a specialized software program, or a specialized physical hardware device, or often a combination of both. Its ultimate job is to block unauthorized and unwanted traffic from getting into a computer system.

Having a firewall at home is smart. You may choose to employ a software firewall like "Zone Alarm". You may also choose to install a hardware firewall "router", or use a combination of both hardware and software.

Examples of the software-only firewall: Zone Alarm, Sygate, Kerio.
Examples of a hardware firewall: Linksys, D-Link, Netgear.
Note: makers of some popular antivirus programs also offer software firewall as one security suite.
Example: AVG Anti-Virus plus Firewall Edition.

Also Known As: "sacrificial lamb server", "sniper", "watchdog", "sentry"