I don't know the specifics of etherum, I actually do think they are somewhat robust against the more trivial attacks. However, in some blockchains it is absolu

I don't know the specifics of etherum, I actually do think they are somewhat robust against the more trivial attacks. However, in some blockchains it is absolutely feasible to become a majority miner for a short period of time by simply renting cloud resources. If the network is further temporarily reduced due to internet connectivity flapping/segmentation, it might be cheap. 1) Situate yourself in a country with poor connectivity. 2) Trip a breaker to zap most of the connectivity 3) Spin up a gazillion cloud instances 4) Compete more-or-less only with national miners.