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Glossary Networking

Firewall

A firewall is a system that allows or blocks network traffic according to rules about addresses, ports and protocols.

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In more detail

Firewalls run in hardware at the edge of a network or as software on a single computer. A good starting policy is to deny everything by default and open only the Ports a service needs. Web application firewalls go further and inspect HTTP requests themselves.

Try these tools

TCP/UDP Port Range Generator

Generate a firewall-rule-ready list of ports from single values and ranges, with automatic compression.

Port Number Lookup

Look up the standard service name for a well-known TCP/UDP port, or search ports by service name.

See also

  • Glossary Port
    A port is a number from 0 to 65535 that tells a computer which program or service an incoming network connection is for.
  • Glossary VPN
    A VPN (virtual private network) creates an encrypted tunnel between your device and another network.
  • Cheat sheet Common Network Ports Cheat Sheet
    The port numbers behind the web, mail, SSH, DNS and databases, with TCP or UDP.
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