Mercado Bitcoin Is Reopening After a Cyberattack Froze Withdrawals for a Week. What Happens to Your Crypto When an Exchange Goes Dark? - 24/7 Wall St.

The cyberattack specifically targeted Mercado Bitcoin's hot wallets and customer deposit addresses, with blockchain security company Hypernative identifying suspicious transactions across at least 10 different blockchains. The exchange has declined to confirm this figure but has committed to using its own funds to replace the affected assets, stating that its trading desk is preparing to begin necessary repurchases in domestic and international markets.

Mercado Bitcoin's handling of this incident may affect how regulators assess its licensing application, particularly regarding compliance with Brazil's Central Bank Resolution BCB 520/2025, which requires reviews of the segregation between a crypto provider's own virtual assets and those owned by customers.

Customer Claims vs. Actual Ownership

Many exchanges use pooled wallets, where a single wallet holds cryptocurrencies for multiple users, while an internal ledger tracks individual ownership. This means a user's balance is essentially a claim on the exchange, not direct ownership of the actual coins. This distinction becomes critical when exchanges face financial trouble.

Our trading desk is preparing to begin the necessary repurchases in domestic and international markets.

Historical Precedents

The situation echoes previous exchange failures. FTX customers were repaid in U.S. dollars based on crypto values at the time of the exchange's bankruptcy in November 2022, meaning Bitcoin holders missed subsequent rallies. Celsius customers fared worse when a federal judge determined that users of its 'Earn' product had given up control of their coins, which then belonged to the bankruptcy pool.

Mt. Gox demonstrates the potential for lengthy waits, with its trustee extending the repayment deadline from October 31, 2026, to October 31, 2027. Mercado Bitcoin's update has not provided a timeline for when withdrawals will resume, nor has it offered a verified account of losses or a reserve check to confirm that available coins match customer balances.

Market Impact

Mercado Bitcoin's freeze hasn't significantly moved Bitcoin's price, which trades at $75,720, down 2.3% over the week and 7.3% over the last month. Bitcoin's market value tops $1.5 trillion, making individual exchange incidents less likely to impact the overall market unless they trigger widespread withdrawals.

Customers may want to review the exchange's terms to see whether they retain ownership of their coins. Many individuals keep only a portion of their holdings on exchanges, using self-custody wallets where they control their private keys. From November 9, Mercado Bitcoin customers can download their statements and take screenshots of their balances as proof for future claims.