What does "defense in depth" refer to?

"Defense in depth" is a security strategy that emphasizes the use of multiple layers of security controls to protect an organization's assets. By implementing various security measures at different layers, this approach provides a comprehensive defense against potential threats. If one layer is breached, others remain in place to mitigate risks.

This strategy recognizes that no single security measure is sufficient to completely eliminate vulnerabilities. Instead, it combines physical security, network security, application security, and user training, among other measures, to create a robust defense framework. This multifaceted strategy helps to ensure that even if an attacker bypasses one layer of security, additional layers are still in place to defend against intrusion.

In contrast, approaches that rely on a single layer, such as focusing solely on firewalls or enhancing software speed without regard to security, do not provide adequate protection in today’s complex threat landscape. Therefore, the layered approach inherent in "defense in depth" is critical for safeguarding sensitive information and ensuring the integrity of systems.