On Sunday, rumors spread around the community that there had been a double-spend attack on Ethereum Classic. The team behind the project immediately responded to the rumors, to ease investors.

There have been rumors of a possible chain reorganization or double spend attack.

From what we can tell the ETC network is operating normally.

BlockScout’s “Reorg” section shows nothing of the sort.https://t.co/Yi2cXusCz9 pic.twitter.com/HdUtS0DJZK

— Ethereum Classic (@eth_classic) January 6, 2019

Since Sunday, the Ethereum Classic attack has been confirmed, and the culprit has fessed up. During the week, the devs behind the project asked exchanges and pools to significantly increase their ETC confirmation times. Many in the community felt the Ethereum Classic team was trying to downplay the extent of the situation.

To be clear we are making no attempt to hide or downplay recent events.

Facts are facts and as the situation develops we’ll soon get a full picture of what actually took place.
Linzhi is testing ASICS. Coinbase reported double spends; both may be true.

In time we will see. https://t.co/bbq6eqIoiS

— Ethereum Classic (@eth_classic) January 7, 2019

Ethereum Classic Attack Uncovered

The devs behind the project have officially responded with all the information they’ve dug up on the matter and expanded it into two posts.

A community organized call was conducted to go over the main points regarding the recent attacks on ETC, analyze the community reaction, and diagnose possible solutions and next steps.

Post Mortem Meeting Ethereum Classic ETC – Jan. 2019 Reorg Attacks https://t.co/EFvysXST9g

— Ethereum Classic (@eth_classic) January 10, 2019

The other post released most recently and can be seen below.

Attackers address has been flagged & shared with partners to prevent further attack on other exchanges. The identity of the attacker can finally be located if the relevant exchanges are willing to assist.

The analysis of ETC 51% attack from @SlowMist_Team https://t.co/HVFFxmoeTY

— Ethereum Classic (@eth_classic) January 10, 2019

Donald McIntyre wrote a long blog post via Medium regarding the attack and details of the ‘post mortem’ meeting. The blog post by MacIntyre covers the majority of the information on the attack, including the dates, amounts, and who was affected.

The double-spend attack occurred from January 5th to January 7th. The Ethereum Classic attack included at least 15 double spend transactions that had at least 219,500 ETC stolen. Coinbase was the exchange that originally found the attack.

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SlowMist, a team focusing on security of the blockchain identified the culprit addresses that originated from Gate.io and Bitrue.

Gate.io has already confirmed it will cover 40K ETC losses for all of its users that had ETC stolen.

[https://t.co/8kWqgDWNXb Research] confirms the ETC 51% attack.

4 of the 7 rollback transactions detected were created by the attacker; transferring 54,200 ETC in total.

Gate will be covering the 40k ETC loss for all of the users.

See details: https://t.co/BhEYHZyP3z pic.twitter.com/pSXrsZrc7q

— gate.io Exchange (@gate_io) January 8, 2019

During the meeting, the team behind Ethereum Classic discussed how to prevent this from happening again and steps to take if it does occur. There was no monitoring system in place to alert the team of the double-spend, and the team has deemed this a top priority.

In addition, the devs behind Ethereum Classic have asked exchanges to increase their confirmation times on the digital token.