Which statement best describes the security onion analogy for defense in depth?

Which statement best describes the security onion analogy for defense in depth?

• A. Firewalls alone provide sufficient defense
• B. All layers of the onion must be penetrated to gain access to vulnerable assets
• C. If one layer fails, all layers are compromised
• D. Users must authenticate twice before accessing assets

Answer: (B)

Defense in depth relies on multiple, overlapping layers of security so that bypassing one layer doesn’t automatically give access to everything. The onion analogy imagines assets surrounded by several rings of protection, each one harder to breach than the last. To reach the assets, an attacker would have to penetrate every layer, not just one. That’s why the statement describing that all layers must be penetrated best captures the idea: each ring stands as a separate barrier, contributing to overall security. It’s also helpful to note why the other ideas don’t fit as well. Relying on firewalls alone ignores the other layers that protect systems and data. The notion of needing to authenticate twice is a specific control scenario, not the broad layered approach the onion analogy conveys. And while defense in depth means a single layer failure doesn’t guarantee total compromise, the core point of the onion concept is that access requires overcoming each successive layer.

Defense in depth relies on multiple, overlapping layers of security so that bypassing one layer doesn’t automatically give access to everything. The onion analogy imagines assets surrounded by several rings of protection, each one harder to breach than the last. To reach the assets, an attacker would have to penetrate every layer, not just one. That’s why the statement describing that all layers must be penetrated best captures the idea: each ring stands as a separate barrier, contributing to overall security.

It’s also helpful to note why the other ideas don’t fit as well. Relying on firewalls alone ignores the other layers that protect systems and data. The notion of needing to authenticate twice is a specific control scenario, not the broad layered approach the onion analogy conveys. And while defense in depth means a single layer failure doesn’t guarantee total compromise, the core point of the onion concept is that access requires overcoming each successive layer.