Bitfinex lost 119,756 BTC through a multisig wallet exploit, with funds dormant for years before being traced and seized.
Hackers exploited a vulnerability in Bitfinex's multisig wallet setup with BitGo, draining 119,756 BTC across 2,072 transactions. The exact exploit mechanism was never fully disclosed. Bitfinex socialized losses by reducing all customer balances by 36% and issuing BFX tokens as IOUs. The exchange eventually repaid all customers.
Funds sat largely dormant for over 5 years. In February 2022, the US DOJ arrested Ilya Lichtenstein and Heather Morgan, seizing 94,636 BTC — the largest crypto seizure in history at the time. Funds had been laundered through darknet markets, BTC mixers, and AlphaBay. Lichtenstein pleaded guilty to money laundering conspiracy.
N/A - 2072 transactions, see DOJ filing