Mining operations overseen by Minero have been centralized
In a shocking turn of events, the mining pool Qubic has reportedly executed a 51% attack on the Monero network between August 11-12, 2025. This attack, according to reports, gave Qubic control over a significant portion of Monero's hashrate, estimated to be between 51% and 65%.
The attack resulted in a six-block chain reorganization, orphaning around 60 blocks. This event, characterised by Qubic as a demonstration of its "Useful Proof-of-Work" (UPoW) model, has raised concerns about the security and integrity of the Monero network.
The economic impact of this attack was significant. Monero's price dropped by about 8.6% following the attack, and major exchanges like Kraken temporarily suspended Monero deposits and later required 720 confirmations before crediting deposits.
The potential threats posed by this attack include risks of double-spending, transaction censorship, and rewriting of blockchain history. Although no double-spend or theft was reported, the event highlighted vulnerabilities in proof-of-work consensus for mid-sized cryptocurrencies.
In response, the Monero community has proposed consensus overhauls to defend against future 51% attacks. There are ongoing debates about hash power distribution and the need for stronger protections against such attacks.
Qubic's strategy involved coordinated public announcements, staged takeover "marathons," and substantial hashrate redirection to Monero mining, alongside aggressive tactics such as rejecting other pools’ blocks and enduring DDoS counterattacks by Monero supporters.
It is estimated that the cost of this attack amounts to approximately $75 million per day, as per the Technical Director of Ledger, Charles Guillaume. The large-scale blockchain reorganization also allowed for the rewriting of the Monero network's transaction history.
It is important to note that the Monero network, despite being privacy-focused, is not immune to 51% attacks. This incident underscores that even coins like Monero, using proof-of-work security, remain vulnerable to coordinated hashrate concentration by large mining entities.
The crypto community is now renewing efforts to implement stronger protections against 51% attacks and raise awareness about mining pool centralization risks. It is crucial for related platforms to remain vigilant and monitor the situation closely.
[1] Source: CoinDesk [2] Source: The Block [3] Source: Decrypt [4] Source: Cointelegraph [5] Source: Forbes
Technology plays a critical role in the execution of a 51% attack, as demonstrated by Qubic's utilization of coordinated public announcements, staged takeover "marathons," and substantial hashrate redirection to Monero mining. The economic consequences of such an attack are significant, with Monero's price drop and temporary suspensions on major exchanges being part of the fallout. However, this incident underscores the vulnerability of even privacy-focused networks like Monero to 51% attacks, emphasizing the need for stronger technological protections against targeted hashrate concentration.
