Ethereum Classic is using an idea Vitalik Buterin had in 2014 to help fend off 51% attackers. Over the past weekend, on block 11380000, a solution for the prevention of 51% attacks was introduced to the Ethereum Classic (ETC) community. Several such attacks have recently placed ETC at a crossroads, leaving the very survival of the chain uncertain. In the weeks that followed these attacks, the community worked to evaluate numerous potential solutions.
Visit here:
https://cointelegraph.com/news/things-just-got-messy-for-potential-ethereum-classic-51-attackers