Monero faces critical 51% attack as Qubic controls network hash power

Monero (XMR), one of the most prominent privacy-focused cryptocurrencies, has been hit by a critical 51% attack, as a mining group known as Qubic has reportedly gained control of over 51% of the network’s hash power. The event has sparked concerns over the security and decentralization of the blockchain, with the XMR price dropping nearly 9% in the aftermath [1].

Sergey Ivancheglo, known in the crypto space as “Come-from-Beyond” (CFB), announced on X on August 12 that Qubic had surpassed the 51% threshold on Monero’s network. “Looks like Qubic has achieved 51% over Monero, we are waiting for independent confirmations,” he stated. Charles Guillemet, CTO of Ledger, later confirmed the claim, noting that Qubic now controls the majority of Monero’s computing power. He warned that this dominance could enable large-scale blockchain rewrites, double-spending, and transaction censorship [1].

Guillemet emphasized that with Qubic’s control, other miners have little incentive to continue operations, as the group can simply orphan competing blocks, effectively becoming the sole miner. He estimated the daily operational costs of the attack at around $75 million but noted that the operation could still be profitable in the short term. “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,” he added [1].

Despite the alarming implications, CFB claimed the takeover was not malicious but rather an effort to prepare Monero for future attacks. He suggested the move was intended to help the privacy coin strengthen its defenses against potential threats. “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 have helped Monero to prepare for its future fights against those agencies?” CFB wrote [1].

Qubic’s strategy has centered on an incentive-driven “pay-to-switch” mining campaign. By offering significantly higher payouts than regular Monero mining pools, Qubic attracted enough participants to surpass the 51% threshold. According to data from Chaos Labs, Monero’s hash rate climbed to 3.01 GH/s as miners chased higher rewards—$3.13 per day compared to $0.64 from standard pools. Over the past 30 days, this led to a 28% drop in XMR’s price, while QUBIC tokens surged 57% [1].

The model also involves splitting mining profits: half is distributed to participating miners, while the other half is used to purchase and burn QUBIC tokens. For instance, if Qubic mines 100% of Monero’s daily blocks, it yields around 432 XMR—approximately $118,000 at current prices—with $59,000 burned daily [1].

However, the attack has also raised questions about the true ownership of Monero’s hash power. The network’s privacy focus makes it difficult to verify hashrate ownership, as stealth hashrate does not appear on public dashboards that label ownership. CFB, a Qubic developer, confirmed the hashrate quota, but the lack of transparency has fueled ongoing debate about the legitimacy and implications of the attack [1].

Source: [1] Monero hit by critical 51% attack as Qubic gains control of network (https://cryptoslate.com/monero-hit-by-critical-51-attack-as-qubic-gains-control-of-network/)