defense-in-depth

Defense-in-depth is a security and reliability engineering construct in which multiple, independent layers of protection or failure mitigation are deployed so that the compromise or failure of any single layer does not lead to system breach or collapse. Its parameters are: (1) layered architecture with distinct controls at each tier, (2) functional independence between layers — a cause that defeats one layer does not defeat others, and (3) progressive resistance — an attacker or fault must overcome each layer in sequence, increasing cost, detection probability, and likelihood of failure. It persists through documented engineering standards, architectural reviews, and compliance audits that mandate layer placement and independence testing. [formal: praesidium | substrate: behavior | horizon: a life | explicit: yes | epoch: 0.01]