Quote from: CrypTrends on October 18, 2017, 09:21:40 PM

can you explain in simple words with is 51% attack?
can it happen also in altcoins?
and if case it happend, and someone do this attack, for how long he will be able to influence the market? is it only untill a new block will be created in the blockchain?

Here's my very very high-level understanding of it (someone please correct me if I'm wrong and add to it).

Basically, every block has to be confirmed by a majority of the network to ensure an orderly blockchain (each block needs to be validated by the rest of the network). If a single entity controls more than 50% of the network hash power, they theoretically have the ability to determine which blocks are considered valid, and thus can form the chain as they choose.

That's not a great explanation, but it's something to build off of.