Arkham Traced $3.5 Billion Bitcoin Theft Hidden for Years

Arkham Intelligence Traced $3.5 Billion Bitcoin Theft Hidden for Years

Written by Aaron S.,

Editor-In-Chief

Last Updated: August 04, 2025

Key Takeaways

LuBian lost 127,426 BTC in a 2020 hack that stayed hidden until Arkham Intelligence uncovered it on August 2, 2025;
The mining pool tried to warn the thief via 1,516 blockchain messages but never reported the breach;
Arkham noted that weak private key generation made it possible for hackers to brute-force LuBian’s wallets.

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Arkham Intelligence, a blockchain analytics firm, reported that it identified a Bitcoin theft that went unnoticed for years on August 2.

On December 28, 2020, a Chinese Bitcoin mining group called LuBian lost 127,426 BTC BTC $112,034.96 in an attack that was never made public.

At the time, that amount was worth about $3.5 billion, which made it the biggest known crypto-related theft to date. LuBian was a large player in the crypto mining industry back then, and ranked as the sixth-largest Bitcoin mining pool.

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Most of the group’s Bitcoin was taken before the company could react. LuBian eventually moved just under 12,000 BTC into separate wallets to prevent further losses.

Following the theft, LuBian left messages on the blockchain addressed to the attacker. These messages were sent in 1,516 separate transactions, each including a short OP_RETURN note directed at the hacker’s wallet addresses.

In total, LuBian spent around 1.4 BTC to post these warnings. The messages did not stop the theft, but helped Arkham Intelligence trace the stolen funds years later.

Arkham Intelligence also found clues about how the attack may have happened. Their team said:

It appears that LuBian was using an algorithm to generate its private keys that was susceptible to brute-force attacks. This may have been the vulnerability exploited by the hackers.

On July 15, Aracadia Finance was targeted in an attack that led to the loss of around $3.5 million in crypto assets. How did it happen? Read the full story.