Ethereum Classic Hit by Third 51% Attack in a Month

August has been an awful month for Ethereum Classic as the blockchain suffered yet another 51% attack.

AccessTimeIconAug 29, 2020 at 11:00 p.m. UTC
Updated Sep 14, 2021 at 9:49 a.m. UTC

The Ethereum Classic blockchain suffered a 51% attack Saturday evening, its third such attack this month, noticed by mining company Bitfly, which also spotted the first attack on Aug. 1.

  • The attack reorganized over 7,000 blocks, or two days' worth of mining, according to a tweet shared by Bitfly. The first two attacks reorganized 3,693 and 4,000 blocks respectively.
  • Notably, a leading organization behind the Ethereum Classic network, ETC Labs, announced its strategy to protect the network from additional attacks last week, including defensive mining that is intended to stabilize the network's plummeting hashrate and resist future 51% attacks.
  • Stevan Lohja, technology coordinator at ETC Labs, in a private message with CoinDesk, said he finds the timing of the attack "very suspicious" as it came just a day after a meeting of Ethereum Classic core developers regarding "aggressive innovation" in the blockchain's proof of work.
  • ETC Cooperative, another prominent foundation supporting the network's development, took to Twitter following Saturday's attack saying, "We are aware of today's attack and are working with others to test and evaluate proposed solutions as quickly as possible."
  • After the first two attacks, exchange OKEx responded by saying it will consider delisting the asset due to the network's severe lack of security. Coinbase also took drastic measures by extending deposit and withdrawal confirmation times for ETC to roughly two weeks.
  • Following the latest attack, leading cryptocurrency derivatives exchange FTX will reconsider its ETC perpetual futures contracts, according to CEO Sam Bankman-Fried in a private message to CoinDesk. He said this is so even though FTX doesn't support spot trading and the cryptocurrency network's insecurity has less of a direct effect on the risk of offering futures trading.
  • The cryptocurrency seems largely unaffected by the series of attacks, trading at $6.86 at last check, less than 4% below its price during the second attack. The coin has traded hands between $6 and $8 for nearly the entire month of August.

UPDATE (Aug. 29, 23:03 UTC): Adding comment from ETC Cooperative.
UPDATE (Aug. 30, 01:05 UTC): Adding comment from ETC Labs' technology coordinator.

UPDATE (Aug. 31, 16:59 UTC): Clarifying Lohja's comment in reference to Ethereum Classic core developers, not "Ethereum Core" developers


Please note that our privacy policy, terms of use, cookies, and do not sell my personal information has been updated.

The leader in news and information on cryptocurrency, digital assets and the future of money, CoinDesk is a media outlet that strives for the highest journalistic standards and abides by a strict set of editorial policies. CoinDesk is an independent operating subsidiary of Digital Currency Group, which invests in cryptocurrencies and blockchain startups. As part of their compensation, certain CoinDesk employees, including editorial employees, may receive exposure to DCG equity in the form of stock appreciation rights, which vest over a multi-year period. CoinDesk journalists are not allowed to purchase stock outright in DCG.

Learn more about Consensus 2024, CoinDesk’s longest-running and most influential event that brings together all sides of crypto, blockchain and Web3. Head to to register and buy your pass now.