Brazil's Mercado Bitcoin freezes accounts after security incident; losses near $40M

Brazil's biggest crypto platform kept both deposits and withdrawals frozen on Monday following a security breach affecting one of its systems. While the company attempted to resume normal operations, clients were left without the ability to move funds into or out of the exchange.

In a statement on X, Mercado Bitcoin confirmed that the incident had been identified and contained. The exchange asserted that no customer funds were lost and no data was compromised, calling the freeze a precautionary step. It added that its teams are conducting investigations, tracking assets, and working with law enforcement. Bloomberg reported that the firm plans to cover any losses itself.

Mercado Bitcoin has not disclosed which system was compromised, the amount stolen, or a timeline for reopening. So far, its announcements have omitted both a total loss amount and a specific reopening date.

The exchange later released destination addresses related to transactions from the incident, spanning Bitcoin, Ethereum-compatible blockchains, Solana, Stellar, and Tron. It stated that the addresses were shared to aid identification and tracking. Blockchain security firm Hypernative has provided an early assessment suggesting suspicious transfers exceeding $40 million across multiple chains. Mercado Bitcoin has not verified that number.

Some analysts are pointing to even larger amounts and note that asset sweeps are still in progress.

Tether has joined the response effort. CEO Paolo Ardoino announced on X at 10:06 a.m. ET that more than 4.5 million USDT tied to the incident had been frozen. Tether previously invested $20 million in Mercado Bitcoin in July, at which time the exchange claimed 4.5 million users.

A rough week for Mercado and other exchanges

This event follows closely after one of the biggest cryptocurrency heists in recent times. On Oct. 29, attackers accessed $6.3 billion in Binance assets by compromising an engineer's laptop and breaching internal systems responsible for processing withdrawals.

Binance reported that no private keys were compromised. By Nov. 1, it had recovered 95 percent of the stolen funds and started a phased restoration of withdrawals.

The FBI has linked the attack to North Korea. Meanwhile, the U.S. Secret Service is cooperating with Circle to track and freeze assets. Tether said approximately $1.57 billion in USDT had been frozen, and Circle reported freezing more than $800 million in USDC with law enforcement help.

Binance stated that it discovered additional breach points beyond the original compromise, which it had initially blamed on one engineer's laptop. The exchange has yet to release a comprehensive post-mortem detailing how the attackers planned and carried out the theft, which some sources say required at least 36 hours of preparation.

The whereabouts of approximately $3.3 billion in stolen assets that avoided being frozen remain unclear, and Binance has not specified how much it anticipates recovering from that portion. Law enforcement and investigators are still monitoring wallet movements across ten blockchains.