Blockchain “de-anonymizer” firm Arkham has discovered what it believes is the biggest Bitcoin (BTC) hack in history.

In a post on the social media platform X, Arkham says it has uncovered the “largest ever” BTC hack, which appears to have targeted Chinese mining firm LuBian in 2020.

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While the firm has never publicly acknowledged the hack, Arkham’s on-chain analysis suggests that 127,426 BTC was stolen from LuBian in December of 2020, which was worth $3.5 billion at the time and is now worth about $14.5 billion.

“LuBian was one of the world’s largest mining pools in 2020, controlling almost 6 of the Bitcoin network’s total hash-rate as of May 2020.

They appear to have been first hacked on December 28th, 2020 for over 90 of their BTC. Subsequently, on December 29th, around $6 million of additional BTC & USDT was stolen from a LuBian address active on Bitcoin Omni layer.

On the 31st, LuBian rotated their remaining funds to recovery wallets.”

Arkham also discovered on-chain messages between LuBian and the hackers’ wallet addresses offering a reward if they acted as whitehats – hackers that take a payment in exchange for discovering security weaknesses and returning the stolen funds.

“To the whitehat who is saving our asset, you can contact us through 1228btc@gmail.com to discuss the return of asset and your reward.”

Arkham says it appears that LuBian had used an algorithm to generate its private keys for custody of its coins, which may have been vulnerable to brute force exploits.

For now, the hacker still holds the coins, which were last moved in July of 2024, according to Arkham.

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