Coinbase suspended Ethereum Classic (ETC) trading after a successful 51% attack

The cryptocurrency exchange Coinbase suspended the trading of Ethereum Classic (ETC) after double-spend attacks worth $1.1 Million

The cryptocurrency exchange Coinbase has suspended the trading of Ethereum Classic (ETC) after double-spend attacks that consist in spending digital coins twice.
Ethereum Classic (ETC) is the original unforked Ethereum blockchain, the attacks resulted in the loss of $1.1 million worth of the digital currency.

51% attack refers to an attack on a blockchain by a group of miners that controls over 50% of the network’s mining hashrate.

“On 1/5/2019, Coinbase detected a deep chain reorganization of the Ethereum Classic blockchain that included a double spend. In order to protect customer funds, we immediately paused interactions with the ETC blockchain.” reads a blog post published by Coinbase.

“Subsequent to this event, we detected 8 additional reorganizations that included double spends, totaling 88,500 ETC (~$460,000). Update: Subsequent to this event, we detected 12 additional reorganizations that included double spends, totaling 219,500 ETC (~$1.1M).”

The attackers were able to double spend about 219,500 ETC and transfer them to wallets under their control.

On January 5, the exchange discovered a deep chain reorganization of the Ethereum Classic blockchain, then it halted send/receive interaction with the ETC blockchain in order to safeguard customer funds.

“Due to unstable network conditions on the Ethereum Classic network, we have temporarily disabled all sends and receives for ETC. Buy and sell is not impacted. All other systems are operating normally.” reads an
update published by Coinbase on January 6, 2019.

The price of the Ethereum Classic (ETC) digital currency went down just after the attacks were reportes.

Bitfly, a fellow cryptocurrency trading platform, confirmed the attack and stated that it is still ongoing.

We can confirm that there was a successful 51% attack on the Ethereum Classic (#ETC) network with multiple 100+ block reorganization. We recommend all services to closely monitored the chain and significantly increase required confirmations.

— Bitfly (@etherchain_org) January 7, 2019

It is curious to note that Ethereum Classic was not able to defect the attack first and rejected the initial report from Coinbase.

The incident was confirmed later and confirmed that the investigation is still ongoing.

https://twitter.com/eth_classic/status/1082313711027507200

Stay tuned …

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Pierluigi Paganini

(SecurityAffairs – virtual currency, hacking)

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