Ethereum Classic had gone through a 51% attack which amounted to around 54,200 ETC being traded and rolled back. Ethereum Classic is one of the top 20 cryptocurrencies out there based on Market Cap. According to their website:

Ethereum Classic (ETC) is a smarter blockchain, it is a network, a community, and a cryptocurrency that takes digital assets further. In addition to allowing people to send value to each other, ETC allows for complex contracts that operate autonomously and cannot be modified or censored.

But still, like all Proof Of Work Crypto out there, each crypto including even the Big Brother, Bitcoin is also susceptible to 51% Attack. A 51% Attack is a type of attack, where a single/group of people with same motive having at least 51% of the network hashrate, attacks the network for their cause.

The above though looked like a bad factor, is a validation that it is decentralised. As said by Charlie Lee:

“By definition, a decentralized cryptocurrency must be susceptible to 51% attacks whether by hashrate, stake, and/or other permissionlessly-acquirable resources. If a crypto can’t be 51% attacked, it is permissioned and centralized.”

And that is what recently happened to Ethereum Classic. Gate.io Research confirmed the 51% attack on ETC. In the analysis, Gate.io detected 7 rollback transactions. The attacker created four of them, transferring a total of 54,200 ETC. The txhash of the for transactions are

0xb5e074866653670f93e9fd2d5f414672df9f5c21baa12b83686e136444796338
0xee31dffb660484b60f66e74a51e020bc9d75311d246f4636c0eabb9fdf161577
0xb9a30cee4ff91e7c6234a0aa288091939482a623b6982a37836910bb18aca655
0x9ae83e6fc48f63162b54c8023c7a9a55d01b7085294fb4a6703783e76b1b492a

It happened between 0:40 Jan.7, 2019 and Jan 4:20 Jan.7, 2019 UTC for about 4 hours. All the transactions were confirmed usually on the ETC blockchain and became invalid after the blockchain rollback. Three of the attacker’s ETC accounts are identified as follows:

0xb71d9CD39b68a08660dCd27B3EAE1c13C1267B10
0x3ccc8f7415e09bead930dc2b23617bd39ced2c06
0x090a4a238db45d9348cb89a356ca5aba89c75256

Due to the recent events, Gate.io has raised the ETC confirmation number to 500 and launched a new strict 51% detect for enhanced protection. It has also mentioned that:

Gate.io will take all the loss for the users.

The SlowMist team has done a detailed analysis of the same.

Update: 12 January 2019

Gate.io got back 100k USD Value Of ETC from the ETC 51% Attacker as per a report posted on their own blog. They also reminded the public that: “If the attacker didn’t run it for profit, he might be a white (hat) hacker who wanted to remind people (of) the risks in blockchain consensus and hashing power security