Monero hit by critical 51% attack as Qubic gains control of network

The privacy-focused Monero blockchain has suffered a 51% attack, meaning the network is not controlled by a single entity. XMR dropped just shy of 9% after developers flagged the event.

On Aug. 12, Sergey Ivancheglo, known in the crypto community as “Come-from-Beyond” (CFB), claimed on X that Qubic had surpassed 51% of Monero’s network hash rate, saying:

“Looks like Qubic has achieved 51% over Monero, we are waiting for independent confirmations.”

Ledger CTO Charles Guillemet later confirmed the claim, stating that Qubic now controls most of Monero’s computing power.

He noted:

“Other miners are left with no incentive to continue, as Qubic can simply orphan any competing blocks, effectively becoming the sole miner.”

He warned that the group’s dominance could enable large-scale blockchain rewrites, double-spending, and transaction censorship.

Qubic’s 51% Attack on Monero (Source: Evilcos/X)

Guillemet estimated the operation costs around $75 million per day but noted it could still be profitable, at least in the short term.

The Ledger CTO concluded that the attack had allowed a smaller chain to overtake a top 30 crypto tokens. He wrote:

“In effect, a $300 million market-cap chain is taking over a $6 billion one. Monero’s options for recovery are limited, and a full takeover is now possible and even likely.”

However, CFB claimed that the takeover of the privacy-focused network was designed to prepare it against future attacks of such nature.

According to him:

“The Monero team is polishing details of their 51% attack protection. Many accused us of being sponsored by 3-letter agencies to attack this anon coin. What do you think now, after we has helped Monero to prepare for its future fights against those agencies.”

How Qubic gained control of Monero

Qubic’s strategy revolved around an incentive-driven “pay-to-switch” mining campaign.

By offering significantly higher payouts than regular Monero mining pools, the Monero mining pool attracted enough participants to surpass the 51% threshold.

Data from Chaos Labs shows Monero’s hash rate climbing to 3.01 GH/s as miners chased rewards of $3.13 per day compared to $0.64 from standard pools. Over the past 30 days, Qubic’s activity contributed to a 28% drop in XMR’s price over the past month, while QUBIC tokens surged 57%.

Impact of Qubic’s Attack on Monero’s Price (Source: Chaos Labs)

Meanwhile, Qubic’s model also involves distributing half its mining profits to participating miners and using the other half to purchase and burn QUBIC tokens.

So, if the project mines 100% of Monero’s daily blocks, it yields around 432 XMR, worth approximately $118,000 at current prices, with $59,000 burned daily.

Given Monero’s privacy focus, there is some debate about whether Qubic truly achieved the 51% target. The network’s structure makes it possible to obfuscate hashrate ownership, though CFB, a developer at Qubic, confirmed the hashrate quota. Stealth hashrate won’t show on public dashboards that label ownership.

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