- Qubic pool surpasses 51% Monero hashrate, enabling potential chain reorganizations, double-spend attacks, and transaction censorship.
- Selfish mining strategy suspected, raising concerns about network security and vulnerability to coordinated hashpower-based consensus manipulation.
- XMR price drops 13%, while QUBIC token gains amid speculation and heightened trading activity following network disruption.
Qubic, a mining pool that has steadily increased its share of the network’s computational capacity, briefly gained control of more than half of Monero’s hashrate. This allowed it to carry out a chain reorganization involving six blocks earlier today, raising concerns of a potential full network takeover.
Control of over 51% of a blockchain’s hashrate enables the dominant miner to rewrite transaction history, execute double-spending attacks, and block specific transactions. Qubic’s control, according to several blockchain analysts, could orphan blocks mined by others, leaving no financial incentive for competing miners.
The attack’s cost estimates vary widely. Initial figures suggested $75 million per day, but blockchain security experts such as Charles Guillemet, CTO of Ledger, clarified that this figure relates to purchasing hardware outright. Renting equivalent computational capacity could cost closer to $100,000 per day.
Monero appears to be in the midst of a successful 51% attack.
The privacy-focused blockchain, launched in 2014 and long targeted by governments and 3-letters agencies, is already banned from most major centralized exchanges.
The Qubic mining pool has been amassing hashrate for…
— Charles Guillemet (@P3b7_) August 12, 2025
Qubic halted its reorganization shortly after initiating it, stating that it had “chosen not to take over Monero yet.” The pool also disabled its API during the incident, limiting public verification of its hashrate. These actions have led to uncertainty about Qubic’s true computational power and its operational intentions.
Qubic almost immediately halted its selfish-mining attack on Monero, claiming it had “chosen not to take over Monero yet.” This raises questions about whether they can actually sustain such an attack. During the reorganization, Qubic also disabled its API, fueling suspicion about… https://t.co/wDCSdBfJ4z
— Charles Guillemet (@P3b7_) August 12, 2025
While some Monero developers and traders view the incident as a calculated show of strength by Qubic, others question whether the reorganization qualifies as a complete 51% attack. Several commentators note that mining pools with as little as 2% of the hashrate could, by statistical variance, mine several consecutive blocks. Others believe Qubic used a selfish mining strategy, which requires less than 51% but still allows for targeted reorganizations.
The market response has been immediate
Reports suggest Monero’s price has dropped by around 13% since the event, reflecting reduced confidence in network security. Meanwhile, the QUBIC token has experienced a modest increase in value, likely driven by heightened visibility and speculation about the pool’s next steps.
Here a member of the Qubic team @P3b7_. Instead of speculating about Qubic’s motives, you could spend one minute reading our statement, where we explain the reason https://t.co/9S73Ej5pWv.
The purpose here isn’t rivalry or to harm the Monero protocol, its community, or its… pic.twitter.com/lL1Q9zvxA9
— Alber ױ (@albefero) August 12, 2025
Economically, Qubic’s mining strategy links Monero block rewards to its own token’s market activity. Using a model it calls “Useful Proof of Work” the pool converts mined Monero into USDT and uses those funds to buy and burn QUBIC tokens. This process has drawn miners seeking predictable payouts, which in turn concentrates more hashing power under Qubic’s control.
Ledger’s CTO claims sustaining the alleged 51% attack on Monero via Qubic costs $75M/day.
Off by about three orders of magnitude.
Monero’s actual daily security budget is simple to calculate:
– Tail emission of 0.6 XMR per block
– 720 blocks per day (2-minute intervals)
– XMR… https://t.co/m19sRycHkI— ddadybayo (@ddadybayo) August 12, 2025
Qubic’s stated position, expressed through public posts from its members, frames the incident as an “experiment” aimed at stress-testing Monero’s resilience and identifying vulnerabilities. They also suggest their long-term goal involves training artificial intelligence systems with their accumulated computing resources.
