Brazil’s largest cryptocurrency exchange, Mercado Bitcoin, has suspended deposits and withdrawals after a security incident triggered more than $40 million in suspicious crypto transfers, according to blockchain security researchers.
The exchange said it had identified and contained the incident early on Monday, November 2, and temporarily halted transactions as a precaution while investigating the breach. It also assured users that customers had suffered no losses and that no data had been leaked.
However, the exchange has not confirmed the estimated financial impact or disclosed how the attacker gained access to its systems. Blockchain security firm Hypernative flagged more than $40 million in suspicious transfers across at least 10 blockchain networks. Arkham Intelligence data cited by The Block put the amount at approximately $46.3 million.
Mercado Bitcoin investigates suspicious transfers
According to blockchain researchers, wallets associated with Mercado Bitcoin transferred crypto assets to newly created addresses across several networks, including Bitcoin, Ethereum, Solana, Tron, Polygon, Avalanche and BNB Smart Chain.
The transactions appeared to be regular cryptocurrency transfers rather than a direct attack on a smart contract. Researchers have not established how the attacker obtained the ability to move the assets.
Mercado Bitcoin subsequently published destination wallet addresses linked to the incident to help other industry participants identify and track the funds. Its investigation is ongoing, and the exchange has not announced when deposits and withdrawals will resume.
Tether freezes more than 4.5 million USDT
Stablecoin issuer Tether has also taken action in response to the incident. Tether CEO Paolo Ardoino said the company froze more than 4.5 million USDT linked to the suspicious activity.
USDT is a stablecoin designed to maintain a value close to one US dollar. Tether can freeze tokens held at specific blockchain addresses, preventing them from being transferred. However, freezing these assets does not automatically mean they have been returned to Mercado Bitcoin.
Another security incident after the Binance breach
The incident comes days after Binance suffered a major security breach with an estimated impact of $6.3 billion. The FBI has attributed that attack to North Korea, identifying the operation as TraderTraitor.
There is currently no public evidence connecting the Mercado Bitcoin incident to the Binance attack. The two incidents should therefore be treated as separate investigations unless further evidence establishes a link.
For now, Mercado Bitcoin says it is investigating the incident, tracing the assets and coordinating with the relevant authorities. The exchange has yet to confirm the total value involved or provide a timeline for restoring deposits and withdrawals.
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