What Are These Devices? Three different network security devices that control and inspect internet traffic, each operating at different layers and serving different purposes.
1. Network Firewall Physical or virtual device at network perimeter that blocks/allows traffic based on IP, port, and protocol.
Key Characteristics Layer: 3-4 (Network/Transport Layer)
Location: On-premises, between internal network and internet
Type: Physical appliance or virtual machine
Purpose: Control which connections are allowed
What It Checks ✓ Source IP address ✓ Destination IP address ✓ Port number (80, 443, 22, etc.) ✓ Protocol (TCP, UDP, ICMP) ✗ Cannot see HTTP headers ✗ Cannot see URLs ✗ Cannot see content Example Decision Rule: Allow port 443 (HTTPS) to any destination Request: 192.168.1.100 → 203.0.113.50:443 Decision: ALLOW (port 443 is allowed) Rule: Block port 22 (SSH) to internet Request: 192.168.1.100 → 203.0.113.50:22 Decision: BLOCK (port 22 is blocked) Common Products Palo Alto Networks PA-Series (physical appliance) Cisco ASA (physical appliance) Fortinet FortiGate (physical appliance) AWS Network Firewall (virtual/cloud) pfSense (software firewall) Physical Deployment [Internet] | [Physical Firewall Appliance] ← Rack-mounted in data center | [Internal Network Switch] | [User Devices] 2. Proxy Server Physical or virtual device that forwards HTTP/HTTPS requests, can inspect and modify content.
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