51 percent attack

CEX.IO exchange responded to the concerns that its mining pool Ghash.io conducted a ‘51% attack’ against the bitcoin network.

Coinbase Halts Ethereum Classic Transactions After the Network Comes Under Attack
January 8th, 2019

Coinbase took to its Twitter to reveal that its internal developers detected a “deep chain reorganization” of the Ethereum Classic (ETC) blockchain. During that ‘reorgs’ nearly $500,000 worth of ethereum classic was spent twice

‘We Will Never Launch a 51% Attack Against Bitcoin,’ Says Ghash.io
June 16th, 2014

CEX.IO exchange responded to the concerns that its mining pool Ghash.io conducted a “51% attack” against the bitcoin network.