Information security is inherently asymmetric in offense vs defense: Offense needs only one hole, whereas defense needs to plug all, including human behaviors.

Information security is inherently asymmetric in offense vs defense: Offense needs only one hole, whereas defense needs to plug all, including human behaviors. When the offensive side finds a new attack, they can often try and see which of the victim is vulnerable, thus the offense can pick and choose among many potential victims, whereas the defensive side needs to defend from all attackers. The information, once leaked, can't be recovered - i.e. once exploit is successful, there's no "recovery" available. All of those factors combined make defense orders of magnitude more difficult - in terms of careful attention to detail, in terms of manpower, in terms of human training and vigilance, etc. For those reasons, the best defensive strategy is to minimize the information you need to protect.