Updated (August 12, 2025, 1:30pm UTC): This article has been revised to include Qubic’s announcement.
Layer-1 blockchain Qubic has claimed to have completed an effort to gain control of the Monero Network, stating it reached a peak of 51% control over Monero’s hashrate on Monday.
A blog post from Qubic indicated that this “monthly high-stakes technical conflict” concluded with their claimed 51% hashrate attainment. This happened alongside a reorganization of a six-block deep chain that discarded 60 effective blocks.
A deep reorganization, which refers to the process of replacing the last six confirmed blocks with an alternative chain that has greater cumulative work, suggests that Qubic has executed a successful 51% attack on Monero. However, skepticism remains among others regarding this assertion.
Developers dispute the claims of success
Developers quickly challenged these claims, arguing that simply achieving a 51% hash control doesn’t equate to a successful reorganization. Luke Parker, the lead developer at Seraidex, stated in a post on X that the deep six-block reorganization using orphaned blocks “doesn’t imply a 51% attack.”
He further elaborated, saying, “That means adversaries whose massive hash power have had some luck.”
A 51% attack occurs when a single entity controls more than half of a blockchain’s mining power, allowing it to rewrite or fully block transactions. Zhong Chenming, co-founder of the crypto cybersecurity firm Slow Mist, remarked on X that this situation seemed to indicate a successful 51% attack on Monero. However, he noted:
“It’s also costly, and it’s ambiguous what the ultimate economic benefits of this would be. In theory, the Qubic Mining Pool could rewrite the blockchain, double spend, and censor transactions.”
The unfolding of events
Qubic operates on a Layer-1 blockchain that utilizes a “useful proof of work” model, directing mining efforts toward artificial intelligence tasks. Recently, it redirected computing power to target Monero (XMR).
In a blog post from June 30, Qubic announced they had begun promoting Monero CPU mining through their network. The mined XMR is intended to fund Qubic’s ecosystem acquisition and token burns. “Qubic Miners now engage in real-world tasks that generate genuine market value, thereby strengthening the Qubic economy,” the post indicated.
Sergey Ivancheglo, the founder of the crypto projects Qubic, NXT, and IOTA, confirmed that the Qubic network has initiated the acquisition of the Monero Network. He noted in a post on X that after gaining a substantial portion of the network’s hashrate, Qubic started rejecting blocks mined by other pools.
The Monero community responded to Qubic’s economic assault in late July with its own countermeasures, including a distributed denial of service attack against Qubic’s mining pool. During the suspected six-hour DDoS attack, the mining pool’s hashrate plummeted from 2.6 gigahash per second to 0.8 GH/s.
In the midst of this turmoil, Monero’s price dropped about 8.6% to $248, according to Coinmarketcap.
