Monero Under Siege: Qubic Claims 51% Network Control

Qubic Declares Victory in Monero Takeover Attempt

The Monero blockchain is facing a major security scare after Layer-1 project Qubic claimed it successfully gained 51% control of the network’s hashrate. In a Monday blog post, Qubic described the event as the end of a “month-long, high-stakes technical confrontation” aimed at dominating the network. 

The announcement came alongside reports from the Monero Consensus Status dashboard showing a six-block-deep chain reorganization that discarded 60 previously valid blocks. Qubic framed this as proof of a successful 51% attack, declaring its takeover attempt complete.

What the Six-Block Reorg Means

A six-block reorganization happens when the blockchain replaces the last six confirmed blocks with an alternate chain that has more cumulative work. In theory, this is possible when a single entity controls enough mining power to outpace the rest of the network.

Qubic argued that the incident was direct evidence of its network dominance, but several developers pushed back. Luke Parker, lead developer at SeraiDEX, posted on X that a six-block reorg “does not mean a ‘51% attack’ was successful,” adding that it may simply mean “an adversary with a high amount of hash got lucky.”

Experts Split on Whether the Attack Succeeded

While some in the Monero community were skeptical, others believed Qubic’s claim had merit. Zhong Chenming, co-founder of blockchain security firm SlowMist, posted on X:

A 51% attack grants the controlling party the ability to reverse transactions, block new transactions from being confirmed, and potentially double-spend funds — capabilities that could severely undermine network trust.

How Qubic Shifted Its Mining Power to Monero

Qubic, which normally uses a “useful proof-of-work” model to direct computing power toward AI tasks, began rerouting its resources to mine Monero in late June. In a June 30 blog post, the project revealed that it had started incentivizing Monero CPU mining through its own network, with the mined XMR funding buybacks and token burns for the Qubic ecosystem. 

Sergey Ivancheglo, founder of Qubic, NXT, and Iota, openly admitted that Qubic was staging a takeover. He explained on X that once Qubic had control of most of Monero’s hashrate, it would reject blocks mined by other pools.

Monero’s Counterattack and the Hashrate Battle

By late July, the Monero community began mounting countermeasures against what they called an economic attack. These efforts reportedly included a distributed denial-of-service (DDoS) attack on Qubic’s mining pool. During the alleged six-hour DDoS, Qubic’s hashrate dropped sharply from 2.6 GH/s to 0.8 GH/s. 

The network remains operational, but the hashrate war has sparked intense debate about the vulnerabilities of privacy-focused blockchains like Monero. Whether Qubic’s move was a genuine 51% attack or an opportunistic reorg is still up for debate — but the incident has already raised questions about network security, hashrate centralization, and the economic incentives behind such takeovers.