How can a cryptocurrency maintain security amid threats from mining centralization? In August 2025, the Qubic mining pool briefly acquired control of over 51% of Monero’s network hash rate, allowing it to execute a shallow six-block ledger reorganization that temporarily altered the blockchain’s recorded history. Although no full-scale 51% attack with transaction double-spends was observed, this event exposed significant vulnerabilities tied to concentrated mining power in networks with comparatively low hashrates. The incident prompted exchanges such as Kraken to suspend Monero deposits temporarily and impose an increased confirmation requirement of 720 blocks, reflecting a cautious approach to mitigating risks associated with potential chain reorganizations.
Monero’s security framework relies on its RandomX proof-of-work (PoW) algorithm, which is optimized for CPU mining to reduce ASIC miner dominance and foster a more decentralized mining environment. This design lowers the barrier to entry but results in a total network hashrate substantially smaller than that of larger PoW networks like Bitcoin, whose hashrate is measured in exahashes per second compared to Monero’s gigahashes per second. The relatively modest aggregate mining power makes Monero more susceptible to majority control by a single entity or mining pool, increasing the risk of ledger reorganizations and transaction censorship. Such systemic risks inherent in smaller PoW networks highlight the ongoing challenges in maintaining robust security while preserving decentralization. The recent control by Qubic of approximately 38% of hashrate further intensifies concerns around network centralization and potential censorship risks. This event underscored the weaknesses in decentralization and hash rate distribution that can be exploited by large mining pools.
In response, the Monero community has initiated proposals to overhaul the consensus mechanism, including potential integration of ChainLocks—a finality protocol designed to enhance chain stability—and the adoption of merge mining to augment security by leveraging additional hashing power. These measures aim to diversify mining control and mitigate the possibility of any single miner or pool dominating the network’s hash rate, thereby strengthening defenses against double-spends and censorship. Concurrently, recent codebase updates in July 2025 enhanced network stability and privacy protections by fixing vulnerabilities that could expose metadata and compromise anonymity, alongside wallet improvements to improve node communication reliability. These combined efforts underscore Monero’s commitment to addressing its security challenges pragmatically, ensuring continued trust and resilience in the face of evolving threats.
