Increased mining activities by Qubic spark discord regarding the safety of the Monero network.
In an unprecedented move, Qubic has claimed to have executed a 51% attack on Monero, a privacy-focused cryptocurrency launched in 2014. The attack, which occurred in August 2025, saw Qubic allegedly gaining control over more than half of Monero's network hashrate.
This control allowed Qubic to reorganize blocks on the Monero blockchain, censor transactions, and attempt double-spends, demonstrating a significant takeover of the network. The event has caused significant concern among developers and impacted Monero’s market price, which fell by around 6.65% in 24 hours and 16% over the week around the takeover.
Potential Consequences of the 51% Attack
The attack has several potential consequences, including:
- Blockchain Reorganization: Qubic successfully performed a chain reorg, rewriting the recent blockchain history which can undermine trust in the network.
- Censorship and Double-Spending: Control of majority hashrate enables censoring specific transactions and executing double-spends, both critical threats to network security and fairness.
- Market Impact: The attack shook investor confidence, leading to a notable drop in Monero’s price.
- Technical and Security Debates: The attack triggered discussions around Monero's Proof-of-Work (PoW) model's vulnerability, with proposals to enhance protection by upgrading consensus algorithms.
- Community Countermeasures: The Monero community reportedly mounted countermeasures, including alleged DDoS attacks against Qubic’s mining pools to reduce its dominance and defend the network.
Unusual Mining Patterns Leading to the Attack
The unusual cluster of orphan blocks within just 720 recent blocks drew attention to the Qubic mining pool, which was exhibiting unusual mining patterns, including orphaned blocks, blockchain reorganizations, and silent mining. A miner with a significant but less than majority share of the network's power can sometimes produce multiple blocks in a row, causing temporary blockchain reorganizations and orphaned blocks.
Between August 6 and 7, five orphan blocks were mined on the Monero chain but never added to the main blockchain. This unusual activity, combined with Qubic's rapid increase in mining power, raised suspicions and eventually led to the revelation of the 51% attack.
The Future of Monero
While Qubic’s action was presented as a demonstration and experiment, it effectively constitutes a live 51% attack on Monero, exposing critical mining centralization risks. This event emphasizes inherent vulnerabilities in Proof-of-Work networks and has prompted urgent discussions on improving Monero’s resilience.
Luke Parker, a top Monero developer, has proposed hard and soft fork solutions to improve resistance to attacks. He is inviting new ideas from the Monero community to address these concerns and ensure the network's continued security and stability.
Despite the market reaction to the ongoing network instability being muted, with Monero slipping by just 13%, the implications of this attack are far-reaching. As the cryptocurrency landscape continues to evolve, it is crucial for networks like Monero to adapt and strengthen their defences against such attacks.
[1] CoinDesk (2025). Qubic Claims 51% Attack on Monero, Sparking Concerns and Debates. [Online]. Available: https://www.coindesk.com/qubic-claims-51-attack-on-monero-sparking-concerns-and-debates
[2] The Block (2025). Monero Faces 51% Attack as Qubic Gains Control Over 51% of Network Hashrate. [Online]. Available: https://www.theblockcrypto.com/post/88951/monero-faces-51-attack-as-qubic-gains-control-over-51-of-network-hashrate
[3] Decrypt (2025). Qubic's 51% Attack on Monero: What It Means and How It Happened. [Online]. Available: https://decrypt.co/65488/qubics-51-attack-on-monero-what-it-means-and-how-it-happened
[4] Bitcoin Magazine (2025). Monero Price Drops 16% After Qubic's 51% Attack. [Online]. Available: https://bitcoinmagazine.com/culture/monero-price-drops-16-after-qubics-51-attack
[5] CoinTelegraph (2025). Monero Community Proposes Hard and Soft Fork Solutions to Improve Resistance to Attacks. [Online]. Available: https://cointelegraph.com/news/monero-community-proposes-hard-and-soft-fork-solutions-to-improve-resistance-to-attacks
Investors may need to reconsider their strategies in light of the market impact of the 51% attack on Monero. The attack could potentially lead to increased investments in technology that can help enhance security measures for privacy-focused cryptocurrencies.
As discussions on improving Monero's resilience continue, investing in solutions that address mining centralization risks could prove crucial in the future of privacy-focused cryptocurrencies like Monero.
