Monero Mayhem: Qubic’s Dazzling 51% Attack Showcase
Key Takeaways
• Qubic’s uPoW mechanism enabled miners to simultaneously mine Monero while earning multiple revenue streams.
• Its economic model sold mined XMR for USDT, used to buy back and burn Qubic tokens, boosting token value and attracting hashpower.
• In two months, Qubic’s Monero hashrate share rose from 10% to 40%, eventually surpassing 51%.
• Despite Qubic’s claim of no malicious intent, API shutdowns and lack of technical proof raised skepticism.
• 51% attacks remain a critical threat to PoW chains, highlighting how miner incentives can directly impact network security.
On August 12, decentralized computing platform Qubic claimed on social media that it had successfully acquired over 51% of Monero’s total network hashrate—gaining control of the entire network. A 51% hashrate attack is a widely discussed vulnerability in Proof-of-Work (PoW) networks. Although Qubic asserted this was merely a “demonstration for showmanship,” the incident serves as a stark reminder of the risks still inherent in PoW systems.
What is a 51% Hashrate Attack?
A 51% attack occurs when a single entity or group controls over half of a PoW blockchain’s total computational power. This dominance allows them to manipulate the blockchain by executing double-spend attacks, reversing confirmed transactions, and even rewriting chain history—undermining the fundamental trust in the network. While the costs of launching such an attack are typically prohibitively high due to the immense computing resources required, they are not impossible.
How Did Qubic Pull Off Such an Expensive Attack?
Qubic is itself a PoW-based network, but it introduced a novel consensus mechanism called Useful Proof-of-Work (uPoW). Unlike traditional PoW that focuses solely on block validation, uPoW aims for “multi-purpose mining.” It allows miners to simultaneously train AI models, participate in other PoW networks, and fulfill their base computational tasks—effectively stacking multiple income sources on the same hashpower.
In May 2025, Qubic announced that its miners could now direct their computing power toward Monero (XMR) mining. In just one month, Qubic’s miners contributed 10% of Monero’s total network hashrate. Within two months, this figure reached 20%. By the end of July, Qubic-controlled hashpower accounted for a staggering 40% of Monero’s total mining power. Qubic was rapidly swallowing the Monero network.
The core driving force behind this rise was Qubic’s economic incentive design, which offered significantly higher rewards:
- The XMR mined through Qubic was automatically sold for USDT
- The USDT was then used to buy back and burn Qubic’s native token;
- This deflationary cycle drove up Qubic’s token price.
By late July, Qubic miners were earning 3x more than traditional Monero miners—giving them little reason to stay outside the Qubic ecosystem.
As Qubic’s share of the Monero network edged toward the critical 51% threshold, it inevitably drew criticism and even suffered repeated DDoS attacks. In response, Qubic clarified that it was not trying to attack the Monero network, but rather proposing a “mutually beneficial acquisition.” They invited Monero miners to operate via Qubic and even redesigned the incentive model to provide better rewards.
On August 11, after a few suspicious orphaned blocks appeared on the Monero network, Qubic officially declared their Monero acquisition experiment a success. However, the team was quick to clarify: they would not immediately seize control of Monero, pending further evaluation of potential price impact.
So… What Happened in the End?
While Qubic’s move looked flashy, the lack of rigorous technical proof behind their claim cast doubt within the crypto community. Critics questioned both the legitimacy and intent of the so-called “experiment.”
SlowMist founder Cos noted that the only way to truly verify a 51% attack would be to attempt and successfully execute a double-spend, ideally multiple times. Meanwhile, Ledger’s CTO expressed skepticism about Qubic’s motives, pointing out that the platform had disabled its public API, which made independent verification of its hashrate impossible.
Even if Qubic’s intentions were non-malicious, experts remain uneasy. A member of software security firm Trail of Bits warned:“51% attacks, when sustained, are effectively a game-over scenario for chains using Proof-of-Work/Nakamoto Consensus.”
To date, Qubic’s response remains ambiguous. Is this a marketing stunt or a grand social experiment? Only time will tell.
In any case, this event once again reminds us of a crucial truth in crypto: miners are economically driven agents. Beneath the seemingly cold and deterministic code lies a dynamic battleground shaped by human incentives, coordination—and exploitation.
