As quantum computing transitions from theoretical physics to engineering reality, the global cybersecurity landscape faces a systemic threat that cannot be patched overnight. While many view the "Quantum Apocalypse" (or Q-Day) as a distant concern, a sophisticated and silent strategy is already being deployed by nation-states and cybercriminal syndicates: the "Harvest Now, Decrypt Later" (HNDL) attack. The Mechanics of the Silent Theft The HNDL strategy is chillingly simple.