Coinbase Suspends Ethereum Classic After Blockchain History Rewrites

Crypto exchange Coinbase has halted all ethereum classic transactions, withdrawals and deposits due to a series of blockchain history reorganizations on the network.

Ethereum classic saw more than 100 blocks "Reorganized" during a potential 51 percent attack late Sunday, according to at least two different block explorers - Bitfly and Blockscout.

Recent reports from Coinness stated that "Certain abnormality" had been detected in the mining hash rate of a private ethereum classic mining pool.

Blockscout reported block reorganizations occurring at 02:00 UTC and 05:00 UTC Monday, while Bitfly said in a Tweet at 17:00 UTC that the attack was potentially "Ongoing." In its note, Coinbase wrote that "The attacks are ongoing."

Though reiterating to CoinDesk that indeed "a huge reorg took place" on the ethereum classic blockchain, Cravenho's explanation of the event as a 51 percent attack is not widely agreed upon.

In an email to CoinDesk, ethereum classic dev advisor Cody Burns said that the activity could not be labeled a 51 percent attack but rather "a selfish mining attack" caused by a client-local phenomenon.

He added in a post on Twitter that "The entire Ethereum network doesn't 'reorganize' simultaneously. It would be more likely that someone discovered all of Coinbase ETC nodes and 'surrounded' them."

Still, Burns suggested in an email to CoinDesk that regardless of the situation's origin, companies providing services for ethereum classic should take steps to protect their users.

In response to the deep reorg, Kraken announced in an incident report that it was increasing the number of confirmations required to make an ethereum classic deposit.

The ethereum classic Twitter account claimed that the excessive hashrate may have come from crypto miner manufacturer Linzhi, which reportedly confirmed it was testing new machines with a 1,400Mh/s hashrate.