What does the term “defense in depth” refer to?

The term "defense in depth" refers to a strategic approach in cybersecurity and physical security that involves multiple layers of security measures designed to protect an asset. This concept emphasizes that no single security control is sufficient to protect against all potential threats; instead, it combines various security mechanisms to create a more robust defense.

For example, this might include firewalls, intrusion detection systems, antivirus software, and physical security measures like access controls. By layering these defenses, organizations can mitigate risks and make it more difficult for an adversary to succeed at compromising systems or data. If one layer fails, subsequent layers can still provide protection, enhancing the overall security posture.

This contrasts with the idea of relying on a single layer of security, which is often insufficient in the face of sophisticated attacks. The other options do not capture the holistic and redundant nature of defense in depth, focusing instead on narrower aspects of security or emergency procedures that do not encompass the broader strategy of layered defenses.