firewall - MDN Web Docs Glossary: Definitions of Web-related terms 编辑

A firewall is a system that filters network traffic. It can either let it pass or block it, according to some specified rules. For example, it can block incoming connections aimed at a certain port or outgoing connections to a certain IP address.

Firewalls can be as simple as a single piece of software, or more complex, like a dedicated machine whose only function is to act as a firewall.

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General knowledge

• Firewall (computing) on Wikipedia