The combination of high safety and low cost makes SPI firewalls extremely popular.

• A. True
• B. False
• C. Not sure
• D. It depends

Answer: (A)

Stateful inspection keeps track of the state of active connections and makes decisions based on that state. By allowing only packets that belong to an established session and blocking those that don’t, it provides solid protection against common tricks like spoofed packets and unsolicited connection attempts.

This approach delivers meaningful security without the heavy overhead of deeper inspection layers. It’s faster and cheaper to implement than application-layer firewalls or next-generation solutions, yet it still blocks many everyday threats at the network and transport layers. That balance—effective protection at a lower cost and with good performance—helps explain why SPI firewalls are so popular in many networks.

Of course, they don’t automatically catch everything, especially threats inside encrypted traffic or application-level attacks, so in higher-risk environments they’re often complemented with additional controls. Still, for achieving a practical blend of safety and affordability, the statement holds true.