After attacking the Ethereum classic chain on July 31, 2020, the same Attacker attacked the ETC chain again yesterday. The massive reorganization of 4236 blocks happened in Ethereum Classic blockchain at 2020–08–06 02:54:27 UTC.
It affected blocks from 10935623 to 10939858. Attacker mined the first block at 2020–08–05 11:50:20 UTC, so this attack lasted 15 hours and 6 minutes.
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This time attacker was trying to double-spend 465,444 ETC(approx $3.3 M). Based on our investigation, the attacker successfully double-spent 238,306 ETC ($1.68 M) through Bitfinex and another crypto service. In addition, the attacker also got 14.2K ETC as a block reward, which we are not included in our double-spent calculation.
The attacker probably used the same mining source, Nicehash daggerhashimoto, as observed on the following graph.
Attacker, 0x3936968a445b723fdd0c0407efffcaecb07cab19 mined 4236 blocks consecutively, plus some extra blocks after the re-org. The block reward from this attack was, 14,234.30 ETC, which still resides on the attacker’s wallet.
The attack is clearly visible on the miner distribution chart on Bitquery.
This time Attacker included seven transfers in the mined blocks. The total amount of these transactions was 465,444 ETC (approx $3.3 M).
Where the money comes from?
This time the attacker used the money from the first attack, July 31. In our last analysis, we showed how the attacker double spent the money by sending it to Exchange and also his/her own wallet. This time, the attacker used the ETC left from the first attack.
For example the address 0x305292887ad1ffa867e8564c804575f3d7a19a1f is the source of money for the first transaction in the list. This address was used in the first attack. Similarly, other addresses mentioned in the above transaction list also got money from the first attack.
Where the Attacker double-spent this time?
The blocks mined by the attacker included transactions in which the attacker sent his/her money to different wallets controlled by him/her. This activity was not visible to anyone as the attacker did not publish any transactions or the blocks, similar to the last attack.
On the other hand, the chain which was visible to everyone (now reorged and discarded), the attacker first collected the money on the address 0x38cd54fc7b1fe7994355fce1d75c9c4bd7335a46. After that, the attacker distributed money to different addresses.
All these transactions happened during the time of the attack when the attacker silently mined the forked blocks.
Apparently, the final target was some exchanges and other crypto services, and we can find some of them in the following image.
The “fireworks” on the right side of the graph are Exchanges, where Attacker sent the money. The attacker must have converted those ETC into fiat or other cryptocurrencies.
The following address which received money from the attacker belongs to Exchanges and other crypto services.
- 0x618f37d7ff7b140e604172466cd42d1ec35e0544, which we believe, belongs to Bitfinex exchange based on this post, received 143,000 ETC in several transactions. You can find the complete transaction details here.
- 0x9662a0648aa48592a63509c092ab05adf0a84cc9 received 95,650 ETC in multiple transactions. We were not able to identify the crypto service which owns this address. The two biggest transactions, which was received by this address are mentioned below.
Total money loss
Our investigation shows that Bitfinex lost 143K ETC (~$1M) and we were not able to identify the other service mention above who lost 95K ETC (~680K). In total, we were able to able to verify that the attacker profited $1.68M (At least) from this attack.
The mentioned crypto service can identify the attacker based on the above transactions.
We believe the double-spent this time would have been caught. Our transaction monitoring technology, Coinpath®, built to trace blockchain money flow and would have flagged these transactions for further investigation. If you are looking for blockchain transaction monitoring technology, get in touch with us email@example.com.
Note: Special thanks to Yaz Khoury for reviewing the article.
Coinpath® APIs provide blockchain money flow analysis for more than 24 blockchains. With Coinpath’s APIs, you can monitor blockchain transactions, investigate crypto crimes such as bitcoin money laundering, and create crypto forensics tools.
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