Due diligence is a vital part of an investment or acquisition transaction, and most hidden liabilities can be brought to the surface with a little digging. If we ever needed proof that poor security can be damaging to company value: Yahoo lost $350 million in the Verizon acquisition after a string of breaches, and Equifax is expected to pay over $430 million in costs on top of losing about a quarter of its value since its September breach. Yet proactive security due diligence is often neglected.