Technical systems become insecure when the threat model changes. Basically, a system is designed according to the realities of the time. Then, something changes at some point during its use. Whatever the reason, the old security assumptions are no longer true and the system drifts into insecurity. Vulnerabilities that were once unimportant or irrelevant become critical. Vulnerabilities that used to be critical become unimportant. Hacks become easier or harder, more or less profitable, more or less common.
Paradigm Shift
