Coinbase Disables ETC After Double Spend Attack

A leading cryptocurrency exchange has been forced to halt trading of Ethereum Classic (ETC) after spotting double spend attacks amounting to over $1m. San Francisco-based Coinbase first detected the suspicious activity on January 5, noting a “deep chain reorganization of the Ethereum Classic blockchain that included a double spend.” This was followed by another 12 double spends, totalling 219,500 ETC ($1.1m). However, soon after spotting the first reorg, the exchange halted send/receive activity in the blockchain to protect customer funds. Double spend or “51%” attacks are made possible when an entity manages to gain control of more than 50% of a blockchain’s hashrate, meaning they can reverse any transactions they make to respend their cryptocurrency funds. The bigger picture problem is that by gaining majority control of the network, the attacker can raise questions about its integrity. That seems to have been borne out by the sharp drop in the value of ETC over the past 24 hours, although it is now starting to climb again.