A firewall is a software utility or hardware device that acts as a filter for data entering or leaving a network or computer. You could think of a firewall as a security guard that decides who enters or exits a building. A firewall works by blocking or restricting network ports. Firewalls are commonly used to help prevent unauthorized access to both company and home networks.

Software firewalls

Software firewalls are designed to protect a computer by blocking certain programs from sending and receiving information from a local network or the Internet. By default, most programs are blocked by the firewall but can be excluded through the firewall settings.

The image is the icon for Windows Defender Firewall, an example of firewall software included in the Microsoft Windows operating system.

Other software firewall solutions are available through companies like BitDefender, McAfee, Norton, Webroot, and ZoneAlarm.

Hardware firewalls

Hardware firewalls are found on most network routers and can be configured through the router setup screen. The image at the top of this page shows the ZyXEL ZyWALL, a Unified Security Gateway with a firewall and other security features.

  • How to access a home network router setup or console.

Application gateway, Hardware terms, iptables, LFD, Network terms, Port, Port triggering, Security terms, SPI, Stateless, Windows Defender Firewall

  • How to allow a program or game through the Windows Firewall.
  • How to prevent unauthorized computer access.
  • How to enable or disable the Microsoft Windows Firewall.
  • How to disable the firewall program installed on my computer.
  • Description of each category and icon in the Control Panel.
  • Computer security help and support.
  • Network and network card help and support.