Brazil's largest cryptocurrency exchange Mercado Bitcoin suspended deposits and withdrawals on Monday following a security incident in one of its systems. The company said in a statement it had identified and contained the breach but did not disclose which system was compromised or provide a loss figure or reopening timeline.
Mercado Bitcoin said customers suffered no losses and no data leaked, describing the suspension as a precaution. The company stated it would absorb all losses and said its teams are investigating, tracing assets and coordinating with authorities.
The exchange published destination addresses tied to transactions from the incident across Bitcoin, Ethereum-compatible networks, Solana, Stellar and Tron networks for identification and tracking. Blockchain security firm Hypernative estimated preliminary suspicious transfers above $40 million across several blockchains, though the exchange has not confirmed that figure. Other analysts cited higher figures and reported the sweeping continues.
Tether CEO Paolo Ardoino said the stablecoin issuer had frozen more than 4.5 million USDT linked to the incident at 10:06 a.m. ET. Tether invested $20 million in Mercado Bitcoin in July when the exchange reported serving 4.5 million users.
The incident follows a major breach at Binance on Oct. 29 in which attackers reached $6.3 billion in assets after compromising an engineer's laptop. The FBI attributed that attack to North Korea. By Nov. 1, Binance had replaced 95 percent of stolen assets and began restoring withdrawals in phases. Tether froze about $1.57 billion in USDT and Circle froze more than $800 million in USDC in coordination with authorities related to the Binance incident.