Kraken, a centralized cryptocurrency exchange, has temporarily suspended deposits for Monero (XMR) after a confirmed 51% attack on the network on August 12, 2025. The exchange announced the security measure on Friday, August 15, 2025, following the detection of a single mining pool gaining control of more than 50% of the network's total hashing power.
A 51% attack occurs when a single entity or mining pool controls the majority of a blockchain network's hashing power. This dominance allows the attacker to potentially double-spend coins and reorganize transactions on the ledger, compromising the network's security and integrity.
In this instance, the Qubic mining pool reportedly gained control of over half of Monero's hashrate, peaking at 2.6GH/s. This enabled Qubic to reorganize Monero's blockchain six blocks deep, effectively rewriting transaction history and orphaning approximately 60 blocks. Qubic initially faced resistance in its takeover attempt and was allegedly hit with a denial-of-service (DDoS) attack on August 4. A DDoS attack floods a system with fake traffic, preventing legitimate traffic from getting through.
Kraken has taken a "security precaution," stating that Monero deposits have been paused due to the potential risk to network integrity. The exchange is actively monitoring the situation and will resume deposits once it determines it is safe to do so. Trading and withdrawals for XMR remain fully operational on Kraken.
The Monero community has responded to the attack with concern, debating network incentives and security. This 51% attack is considered the first major breach of Monero's consensus protocol, raising concerns about mining concentration and network resilience.
Monero, launched in 2014, is a privacy-focused cryptocurrency that obscures senders, receivers, and transaction amounts, offering greater anonymity than Bitcoin and Ethereum. While its privacy features have driven adoption, Monero's relatively smaller hashrate compared to larger blockchains has made it vulnerable to such attacks. The recent incident highlights the risks associated with concentrated mining pools and their potential to undermine the integrity of privacy-focused networks.
