It seems that the sender of last week's USD 5.28 million transactions has been revealed.
Blockchain analytics and security firm PeckShield claims to have identified the sender - a South Korean peer-to-peer crypto exchange Good Cycle. Furthermore, this small exchange "appears to be a Ponzi Scheme project", claims the firm.
Update: We have identified the victim, a small P2P exchange in Korea called Good Cycle, which appears to be a Ponzi Scheme project. Our investigation found that their security is really lacking, e.g., using HTTP instead of HTTPS, and could be easily hacked.
— PeckShield Inc. (@peckshield) June 16, 2020
Good Cycle confirms that there have been repeated attacks on the exchange.
Last week Cryptonews.com reported on the two transactions with massive fees: first, someone sent ETH 0.55, at the time worth USD 133.93, but paid a whopping ETH 10,669, or USD 2.6 million, in transaction fees. A day later, ETH 350 (USD 86,404) was sent paying the same fee - equivalent to USD 2.64 million.
The transactions went through SparkPool and Ethermine mining pools, which already announced that they will distribute the fee since they hadn't heard from the sender. Several hours ago, two transactions were sent - one to each pool, from the same address the above-mentioned transactions were sent, with a message: "I am the sender."
It's not yet known what the two mining pools plan to do about this. Cryptonews.com contacted them both and will update should they reply. Also, it remains unclear who hacked and allegedly "blackmailed" the exchange.
Meanwhile, Bitfly announced that Ethermine will not interfere in the payout of large transaction fees any longer and will stick with their policy to always distribute the full block rewards. Today they announced that a new safety feature has been introduced to prevent accidental high-fee transactions.
In order to prevent sending txs with a very high fee by accident the Geth team just introduced a new safety feature that will block sending txs with a fee > 1 ETH https://t.co/pyDweUGOT1
Great job @peter_szilagyi
Hopefully other ETH clients will implement a similar feature soon
— Bitfly (@etherchain_org) June 17, 2020