Ethereum Classic Hit by Another 51% attack

Ethereum Classic Hit by Another 51% attack

One of the most severe attacks a blockchain can encounter is the 51% attack. Unfortunately, another 51 percent attack has hit the Ethereum Classic (ETC) network on August 29, making it the third attack this month.

The same attack happened about four weeks ago when a hacker was able to steal cryptocurrency valued at about $7.3 million after launching two consecutive 51% attacks on the Ethereum Classic blockchain.

On August 29, the attack caused over 7,000 blocks to reorganize just weeks after proposing security upgrades. The Ethereum Classic (ETC) Labs came up with a Network Security Plan about two weeks ago, which includes some immediate improvements and several long-term measures. 

The plan includes a high-level measure – switching to a new consensus algorithm capable of reinforcing the security of the blockchain.

The August 29 attack was confirmed in a tweet by Ethereum Classic with a promise to work on possible solutions:

While ETC is still making progress in evaluating proposed solutions, we are aware of the current risk to the network at these low hash rate levels. To miners, exchanges, and other service providers we suggest keeping confirmation requirements levels well above 7K for now.”

The proposed Network Security Plan included the implementation of defensive mining in the short term, requiring the cooperation of miners towards the maintenance of a more consistent hash rate and adjustment if necessary. It highlighted close coordination with exchanges to create a whitelist of addresses and adjust confirmation times.

In a separate tweet on August 29, they noted that ETC is about 3 percent of the general ETH network hashrate and there could be repeated attacks while testing out these changes:

ETC is ~3% of the overall ETH network hashrate. We are well aware of potential repeated attacks while solutions such as “reorg caps” and the subsequent ECIPs are being tested and evaluated. If you haven’t already please increase (which most have) please raise confs above ~10K.” Due to the repeated attack, some exchanges such as OKEx expressed the possibility of delisting ETC if they refuse to improve security.


Born, raised and schooled in Sweden with a degree in law, Glenn is a long time crypto enthusiast. He quickly acknowledged the potential of the blockchain technology, and the benefits of decentralization. Glenn believes in a future where blockchain technology and decentralization will govern and enable people to have a transparent security and financial system.