Cybersecurity Foundations (Grades 9–12) · lesson 2 of 7 · 12 min
What is Defense in Depth? Defense in depth is a layered security strategy. Instead of relying on a single control, you stack multiple independent layers so that if one fails, others still protect the asset. The concept comes from military strategy — slow an attacker down at every layer. The layers Physical: locks, badge readers, security cameras — prevent physical access to hardware. Network: firewalls, IDS/IPS, network segmentation — control traffic between systems. Host: antivirus, host-based firewalls, patch management — protect individual machines. Application: input validation, authentication, authorization — secure the software itself. Data: encryption, access controls, backups — protect the data even if all other layers fail. Human: security awareness training — the most important and most often overlooked layer. No single layer is perfect. Defense in depth assumes breach — it asks “when one layer fails, what stops the attacker next?”
Match the layer to the control
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