If bitcoin network is under heavily attack then you can't open the blockchain in the first place or other site that is connected on that certain attack. This delayed transactions that you are saying is because of the limitation of the size of the blockchain causing traffics inside because of too many transactions that can't be process at a time because it already reached its limits.

Besides bitcoin network can't be hack easily, maybe what you are trying to say is only bitcoin, because millions of dollars of bitcoin has been hacked before on the blockchain by some pro hackers.