Which of the following firewalls inspects the actual contents of packets?

Question

Options

• APacket filtering firewall
• BStateful inspection firewall
• CApplication-level firewall
• DCircuit-level firewall

• A
  2% (1)
• B
  2% (1)
• C
  90% (46)
• D
  6% (3)

Explanation

An application-level firewall (also called an application proxy or layer 7 firewall) operates at the application layer of the OSI model, meaning it can read and analyze the actual payload - HTTP requests, FTP commands, DNS queries - not just headers or connection state. Packet filtering firewalls (A) only examine IP/TCP/UDP headers (source/destination addresses and ports), ignoring content entirely. Stateful inspection firewalls (B) track connection state across packets but still don't parse the payload itself - they know which connection a packet belongs to, not what it's saying. Circuit-level firewalls (D) validate that a TCP handshake is legitimate but also never inspect the data flowing through the circuit after it's established.

Memory tip: Think "A for Application = A for Actual content." The deeper the layer, the deeper the inspection - application layer is the deepest, so it's the only one that sees what's inside the packet.

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