user-1: Has a cryptocurrency network ever been fully DDoSed so that the blockchain did not advance during the attack?
If so, which one and how?

user13645: This is more or less impossible, since you don't know where the miners are. Attacking the major mining pools is feasible, though they deploy some anti-DDoS measures. But even when such an attack would succeed, there still are people non-affected (eg. running behind NAT) and running the *coin network like if nothing happened.
The only issue that I can notice there is that the difficulty for getting a new block would be too high, so that the blocks would be mined much slower.

-1: <p>Has a cryptocurrency network ever been fully DDoSed so that the blockchain did not advance during the attack?</p>

<p>If so, which one and how?</p>
 13645: <p>This is more or less impossible, since you don't know where the miners are. Attacking the major mining pools is feasible, though they deploy some anti-DDoS measures. But even when such an attack would succeed, there still are people non-affected (eg. running behind NAT) and running the *coin network like if nothing happened.</p>

<p>The only issue that I can notice there is that the difficulty for getting a new block would be too high, so that the blocks would be mined much slower.</p>
