How Ethereum Classic Was Saved

All proof-of-work (PoW) cryptocurrencies (of which Bitcoin is one) are vulnerable to the 51% attack. What this means is that an attacker (or miner cartel) with control of 51% of a coin’s mining hashrate has the ability to double spend the attacker’s own transactions, even transactions that have confirmed.

The theory to explain why this doesn’t happen to a coin like Bitcoin is that it is more economically rational for the 51% attacker to simply use that capacity to mine the coin. But there could be other motivations to attack, such as a nation state attack intending to disrupt a coin, or an attempt to thwart an unwanted competing coin even.

Read more here: https://medium.com/@cointastical/how-ethereum-classic-was-saved-for-now-7655e6c36029