Which security control configuration blocks access to a resource in the event of a failure?

Which security control configuration blocks access to a resource in the event of a failure?

• A. Fail-closed
• B. Fail-open
• C. Router firewall
• D. State table

Answer: (A)

Fail-closed means that when the security control experiences a fault, it blocks access by default. This behavior protects the resource even if the control goes down or malfunctions, because the safest default is to deny entry rather than risk an open door. In practice, if a firewall or access-control device fails, a fail-closed configuration will drop traffic, keeping the resource secure. In contrast, fail-open would permit access when the control fails, increasing risk. The other options don’t describe this failure-mode behavior: a router firewall is a device type, not a failure reaction; a state table is a mechanism for tracking connections, not a failure-state policy.

Fail-closed means that when the security control experiences a fault, it blocks access by default. This behavior protects the resource even if the control goes down or malfunctions, because the safest default is to deny entry rather than risk an open door. In practice, if a firewall or access-control device fails, a fail-closed configuration will drop traffic, keeping the resource secure.

In contrast, fail-open would permit access when the control fails, increasing risk. The other options don’t describe this failure-mode behavior: a router firewall is a device type, not a failure reaction; a state table is a mechanism for tracking connections, not a failure-state policy.