Ethereum Classic suffers second 51% attack in a week

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Ethereum Classic (ETC) experienced a 4,000 block org as a result of a 51% attack on August 5—the second block reorg to take place on the network within five days. Although the monetary damage from the latest attack is unknown, if it’s anything like the August 1 incident in which 3,000 blocks were reorged, then you can expect significant monetary losses to the ETC network.

The August 1 attack

The 3,000 block reorg that took place on August 1st was initially thought to be a 51% attack that took place accidentally when a majority of the hash on the ETC network went offline for maintenance. However, a recent analysis of the event from Bitquery has revealed that the August 1st attack was premeditated and resulted in a double-spend of 807,260 ETC (worth roughly $5,765,189 at press time).

According to the Bitquery report, the attacker purchased an amount of hash power from Nicehash provider daggerhashimoto that would give them control of more than 51% of the ETC network. The report says that the attacker spent 17.5 BTC (worth roughly $207,266.50 at press time) for the additional hash; once the attacker controlled a majority of the network, they began double-spending ETC and double-spent over $5.7 million in ETC total. In addition, the attacker mined all of the blocks they reorged and earned an estimated 13,000 ETC (worth roughly $92,821.61 at press time) from mining the block reward.

Was it the same attacker?

Not much is known about the August 5 attack, and if it is anything like the attack that took place on August 1, it will take several days for the details of the attack to be released. Considering it took blockchain analysis companies so long to figure out what actually happened in the August 1st attack, it would not be surprising to learn that the August 5th attack was executed by the same individual using the same method to breach the network.