What does "defense in depth" refer to in cybersecurity?

"Defense in depth" refers to the strategy of employing multiple layers of security controls to protect information and systems. This approach recognizes that no single security measure is foolproof; therefore, implementing a series of defensive mechanisms helps mitigate risks more effectively. By using a combination of technical controls, physical security measures, and organizational processes, an organization can create a more robust security posture.

This philosophy ensures that if one layer of defense is bypassed or fails, additional layers will still provide protection against threats. Examples of these layers include firewalls, intrusion detection systems, antivirus scans, and security policies. Each layer adds an additional hurdle for attackers, significantly increasing the chances of detecting and stopping an intrusion before significant damage occurs.

The other options reflect less comprehensive approaches to security, such as relying on a single solution or focusing exclusively on specific techniques like encryption or user training, which do not encompass the multi-faceted strategy that "defense in depth" advocates.