防火墙 (fáng huǒ qiáng) literally means 'fire-prevention wall' — a compound formed from 防 (fáng, 'to prevent'), 火 (huǒ, 'fire'), and 墙 (qiáng, 'wall'). In computing, it metaphorically refers to a security system that monitors and controls incoming and outgoing network traffic based on predetermined rules. Just as a physical firewall stops fire from spreading between buildings, a digital firewall blocks unauthorized access while allowing legitimate communication.

This term is widely used in IT contexts, cybersecurity discussions, and everyday tech conversations in Chinese. It’s a loanword adaptation — not a direct translation of the English 'firewall', but a culturally resonant calque that leverages familiar imagery. You’ll encounter it in settings like corporate IT policies, home router setups, or software security features.