Which scenario best illustrates the value of defense in depth?

• A. When a single security control fails but other layers still protect
• B. When every control is perfect
• C. When there are no backups
• D. When security is unmanaged

Answer: (A)

Defense in depth relies on multiple security layers so a breach can be stopped even if one control falters. The best scenario to illustrate this value is when a single security control fails but other layers still protect. For example, even if a firewall misses an attack, endpoint protection detects the malware, multi-factor authentication blocks the attacker’s login, data is encrypted so even if accessed it remains unreadable, and regular backups allow recovery after any damage. This redundancy reduces overall risk because no single point of failure determines the outcome.

The other possibilities don’t demonstrate this resilience. If every control were perfect, the concept of redundancy wouldn’t be tested since there’d be no failure to endure. If there are no backups, a breach could still lead to data loss despite other layers, showing a missing defense rather than a demonstration of layered protection. If security is unmanaged, there are no layers to rely on, so the idea of protecting via multiple defenses never comes into play.

So the scenario where one control fails but others continue to protect best shows how defense in depth decreases risk through layered, overlapping safeguards.