Mercado Bitcoin Suspends Deposits and Withdrawals After Security Incident, Losses Estimated Above $40 Million
Brazil's largest crypto exchange, Mercado Bitcoin, halted deposits and withdrawals on Monday after a security incident in one of its systems. Blockchain security firm Hypernative estimates suspicious transfers above $40 million, a figure the exchange has not confirmed.
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What Mercado Bitcoin Has Disclosed
Brazil's largest cryptocurrency exchange kept deposits and withdrawals suspended on Monday after identifying a security incident in one of its systems in the early hours of the day. In statements posted to X, the company said it had contained the incident, that customers suffered no losses and that no data had leaked. It described the suspension as a preventive measure and said it is investigating, tracing assets and coordinating with authorities.
The exchange has not said which system was breached, how much was taken or when it will reopen. According to Bloomberg, the company said it would absorb all losses, but its public statements have not included a total loss figure or a timetable for restoring service.
Competing Loss Estimates
The sources differ on the scale of the problem. Blockchain security firm Hypernative has put preliminary estimates of suspicious transfers above $40 million across several blockchains, including Bitcoin, Ethereum-compatible networks, Solana, Stellar and Tron. Bitcoin Magazine reports that other analysts are citing higher figures and that the sweeping of funds is ongoing. Mercado Bitcoin has not confirmed the $40 million figure or any higher estimate, and the gap between the company's "no customer losses" position and third-party tallies of suspicious flows has not been reconciled in public.
To support tracing, the exchange published destination addresses tied to the incident across five networks, saying the addresses were shared only so others can identify and follow the funds on-chain.
Stablecoin Freezes and Tether's Stake
Tether CEO Paolo Ardoino said on X that the issuer had frozen more than 4.5 million USDT linked to the incident. A freeze blocks the holding addresses from moving the tokens but does not by itself return them to their owner. Tether had invested $20 million in Mercado Bitcoin in July, when the exchange said it served 4.5 million users.
Context: The Binance Theft
The Mercado Bitcoin incident follows a far larger theft at Binance. On October 29, attackers reached $6.3 billion in assets after compromising an engineer's laptop and gaining access to internal withdrawal-processing systems. Binance said it found no evidence that private keys were exposed and had replaced 95% of the stolen assets by November 1, restoring withdrawals in phases. The FBI has attributed that attack to North Korea's TraderTraitor group, and Tether and Circle have reported frozen balances of about $1.57 billion and more than $800 million, respectively. Mercado Bitcoin has not linked its incident to the Binance attack and has not said who is responsible for its own.
Pending questions include how much was taken from Mercado Bitcoin, when service will resume, and whether the exchange's method of entry resembles the Binance breach. The exchange said it will post regular updates on X.
Why It Matters
For Traders
Mercado Bitcoin's withdrawals remain frozen with no reopening date, so any position tied to its Brazilian user base or BRL liquidity faces execution uncertainty.
For Investors
Repeated exchange breaches within days of each other raise the sector-wide custody and operational-security risk premium that institutional allocators weigh.
For Builders
Exchange and wallet teams should review internal access controls and withdrawal-processing permissions, since both recent incidents involved access to internal systems rather than private keys.
This article is for information only and is not financial advice. Read the full disclaimer.
