ETC blockchain recoghnizaion attack cause $1.1M loss in double spends

Coinbase, a cryptocurrency exchange announced at the beginning of this month that the apparent ETC blockchain recognization attack has been accompanied by around half a million dollars in double spends.

From the post:

On 1/5/2019, Coinbase detected a deep chain reorganization of the Ethereum Classic blockchain that included a double spend. In order to protect customer funds, we immediately paused movements of these funds on the ETC blockchain.

At the time of writing, it had been identified at least 9 reorganizations containing double spends, that means, these double spends total sum up to 88,500 ETC or $460,000 at current prices. And it is not a one- time event, so the attacks are apparently going on.

Post from the Firm:

We observed repeated deep reorganizations of the Ethereum Classic blockchain, most of which contained double spends. The total value of the double spends that we have observed thus far is 88,500 ETC (~$460,000).

So, what is the double-spend attack?

The double attacks are directed at cryptocurrency exchanges. Attckers behind this use deposited their funds in the Coinbase for exchange, convert them into another currency then withdraw them finally.

Meanwhile, they managed to create a revised ledger that enabling them to recognize the public ETC blockchain and then publishing it on rest of the network. The Chain reorganization gives potential to the attackers to reverse certain transactions that had been confirmed previously to the network as valid transactions. This will letting them spend the same money twice.

At the same time, they recognize the blockchain’s recent history, and then send their fund that they had previously sent to for the exchange to a wallet in their control.

Customers’ funds are secured

Ethereum Classic responds to Coinbase account of recent events. Below is the section from what it twitted on 8th of Jan

Regarding @coinbase account of recent events: they allegedly detected double spends but unfortunately did not connect with ETC personnel regarding the attack.
This is still very much an ongoing process.