Every packet that crosses your network boundary faces the same five-field interrogation. Understanding what happens in those microseconds reveals why packet filtering remains the foundation of all firewall technology.
Circuit-level gateways verify that conversations start properly without reading what's said—a security philosophy that shaped modern firewalls even as standalone circuit-level gateways disappeared.
Proxy firewalls don't just inspect your traffic—they impersonate you, speaking to servers on your behalf while examining every word you'd say.
Traditional firewalls checked which doors were open. NGFWs look at what's walking through them—identifying applications, inspecting encrypted traffic, and recognizing users regardless of how cleverly traffic disguises itself.
A network firewall checks if you're allowed through the door. A WAF reads what you're carrying. Here's why web applications need both.
The network firewall guards the perimeter. The host-based firewall guards each machine—even from threats already inside your network.
Cloud firewalls flip the security model: instead of guarding network boundaries, they travel with each resource. Learn how security groups, network ACLs, and micro-segmentation protect cloud infrastructure from the inside out.
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