Comment by bonoboTP

Poking one hole in the walls will always be easier than guarding the entire frontier.

To defend properly, you need either either much more formally mathematically verified layers, or always-on online monitoring and intrusion detection running alongside the service. Like the immune system, or like guarding an empire's borders, since you can't put a guard on every meter of border. But you can detect when someone broke in and deploy your soldiers to respond. Currently we are trying to defend by building really hard walls that we hope cannot be pierced anywhere, which isn't realistic.