Mercado Bitcoin, Brazil's largest crypto exchange, suspended deposits and withdrawals on Monday after identifying a security incident in one of its systems, while blockchain security firm Hypernative flagged more than $40 million in suspicious transfers that may be linked to it. The exchange said no customer lost money and no data leaked, and has not confirmed the $40 million figure. Tether chief executive Paolo Ardoino said the stablecoin issuer had frozen more than 4.5 million USDT connected to the incident.
The exchange said in a Portuguese-language statement on X that it had contained the problem. "We identified and quickly contained a security incident in one of our systems early this morning," it said, adding that "as a preventive protection measure, deposits and withdrawals are temporarily suspended." It said it would post regular updates on X. Deposits and withdrawals remained suspended, and the exchange has not given a date for resuming them.
The incident comes days after hackers drained more than $6 billion from Binance on October 29, a theft that Decrypt linked to North Korea's TraderTraitor group, and which CoinDesk put at $6.3 billion. Binance has since reopened withdrawals and said it replenished about 95% of the affected assets. Mercado Bitcoin has not linked the two incidents and has not said who is behind its own.
Hypernative's preliminary analysis spans at least 10 blockchains, including Bitcoin, Ethereum, Solana and Tron, according to Decrypt. Mercado Bitcoin has not disclosed how the attackers got in. In a follow-up post, the exchange published the destination addresses it had identified on five networks: EVM chains, Bitcoin, Solana, Stellar and Tron. It said the addresses were released only so others can identify and track the funds on-chain.
In his post on X, Ardoino wrote: "Tether froze more than 4.5M USDT related to this security incident." USDT is a dollar-pegged stablecoin, and Tether can blacklist the addresses holding it so the tokens cannot be moved, though a freeze does not by itself return the funds to their owner.
Analysis
Why This Matters
- Customers of Brazil's largest crypto exchange cannot move funds in or out while it investigates, with no date given for when deposits and withdrawals will resume.
- Hypernative's preliminary estimate of more than $40 million moved across at least 10 blockchains, unconfirmed by the exchange, points to a loss measured across many networks rather than a single chain.
- Tether's freeze of more than 4.5 million USDT shows a stablecoin issuer acting as an emergency brake on stolen funds, though a freeze does not return them to their owner.
- The episode lands days after the Binance theft, putting exchange security back at the centre of the crypto market.
Background
Mercado Bitcoin is a Brazilian cryptocurrency exchange, described by Decrypt as the country's largest. Crypto exchanges hold customer assets in wallets connected to public blockchains, which makes them a recurring target for attackers; halting deposits and withdrawals is a standard first response while an incident is assessed. Stablecoin issuers such as Tether can blacklist addresses so tokens cannot be moved.
Key Perspectives
Mercado Bitcoin: says it identified and quickly contained a security incident in one of its systems, that no customer lost money and no data leaked, and that deposits and withdrawals are suspended as a preventive protection measure.
Hypernative: its preliminary analysis flagged more than $40 million in suspicious transfers that may be linked to the incident, spanning at least 10 blockchains.
Paolo Ardoino, Tether chief executive: says Tether froze more than 4.5 million USDT related to the security incident.
What to Watch
- When Mercado Bitcoin resumes deposits and withdrawals, and what its promised updates on X disclose.
- Whether the exchange confirms the scale of the transfers Hypernative reported and explains how attackers got into its systems.
- Whether the frozen USDT and the published destination addresses lead to recovery of any funds.
Checked
12 claims in this story checked against 2 sources: 11 supported.
Show each claim
- SupportedMercado Bitcoin suspended deposits and withdrawals on Monday after identifying a security incident in one of its systems.Decrypt: “Brazil's crypto exchange, Mercado Bitcoin, suspended deposits and withdrawals on Monday after identifying a security incident in one of its systems in the early hours of the morning.”
- SupportedMercado Bitcoin is Brazil's largest crypto exchange.Decrypt: “Brazil's Largest Exchange Mercado Bitcoin Halts Withdrawals After $40 Million Hack.”
- SupportedThe exchange said no customer lost money.Decrypt: “The exchange said no customer lost money and no data leaked.”
- SupportedThe exchange said no data leaked.Decrypt: “The exchange said no customer lost money and no data leaked.”
- SupportedHypernative reported more than $40 million in suspicious transfers that may be linked to the incident, across at least 10 blockchains.Decrypt: “Blockchain security firm Hypernative flagged more than $40 million in suspicious transfers that may be linked to the incident, according to a preliminary analysis that spans at least 10 blockchains, including Bitcoin, Ethereum, Solana, and Tron.”
- SupportedThe exchange said, “We identified and quickly contained a security incident in one of our systems early this morning.”Decrypt: “"We identified and quickly contained a security incident in one of our systems early this morning," said in a Portuguese-language statement on X.”
- SupportedThe exchange said, “as a preventive protection measure, deposits and withdrawals are temporarily suspended.”Decrypt: “"As a preventive protection measure, deposits and withdrawals are temporarily suspended."”
- SupportedMercado Bitcoin has not confirmed the $40 million figure.Decrypt: “Mercado Bitcoin has not confirmed that figure”
- SupportedPaolo Ardoino said, “Tether froze more than 4.5M USDT related to this security incident.”Decrypt: “Tether froze more than 4.5M USDT related to this security incident.”
- SupportedHackers drained more than $6 billion from Binance on October 29.Decrypt: “The incident comes days after hackers drained more than $6 billion from Binance on October 29”
- Not in the sourcesDecrypt linked the Binance theft to North Korea's TraderTraitor group.Decrypt: “The incident comes days after hackers drained more than $6 billion from Binance on October 29, a theft the to North Korea's TraderTraitor group.”
- SupportedCoinDesk put the Binance hack at $6.3 billion.CoinDesk: Bitcoin, Ethereum, Crypto News and Price Data: “Brazil’s Mercado Bitcoin halts withdrawals after $40 million drained across 10 chains, days after the $6.3 billion Binance hack.”
