CompTIA Security+ SY0-701 Practice Question

The correct answer is: "When a firewall encounters a failure, it ceases to pass any traffic, effectively isolating the internal network." This is a fail-closed situation. It means that if something breaks, the system shuts down in a safe way, blocking all traffic to keep the network protected.

Here’s why the other choices are wrong:

• "A malfunctioning firewall defaults to allowing all inbound and outbound traffic without restriction." This is fail-open, which is risky because it leaves everything exposed if something goes wrong.
• "A critical server automatically reboots itself..." This is about keeping services running, not about blocking or allowing access.
• "A network monitoring system alerts administrators..." This is just about sending alerts. It doesn't show what happens to the traffic or security when something fails.

Fail-closed means blocking everything to stay safe, and that’s the best choice for security.