Researchers have identified the theft of 127,426 BTC from the LuBian mining pool in December 2020, marking the largest cryptocurrency heist in history with a current value of $3.5 billion. Neither LuBian nor the attacker publicly acknowledged the breach for nearly five years until its discovery in August 2025. Despite the massive loss, on-chain data reveals that LuBian currently retains approximately $605.87 million in Bitcoin holdings. The incident remained completely undisclosed by both parties throughout the intervening period, making it one of the most significant silent security failures in the crypto industry.