the Swiss cheese model
expressionsecuritygovernance & riskops culture
James Reason's accident model: every defense layer has holes, and disasters happen when the holes line up.
Each slice - firewall, review, monitoring, training - is imperfect, which is fine; the design goal is ensuring the holes never align. It is the theory underneath defense in depth, and the honest answer to 'but we had a control for that': you had one slice.
Also known as: Swiss-cheese model