Monero, the main privacy-focused cryptocurrency, is dealing with probably the most severe safety challenges in its historical past.
Qubic, a undertaking led by IOTA co-founder Sergey Ivancheglo, says it now controls greater than 51% of the community’s hashrate. In blockchains secured by proof-of-work algorithms, that is the identical technique utilized by Bitcoin, that stage of management can enable an attacker to rewrite transaction historical past, block transactions or perform double-spend assaults.
In a weblog publish, Quibic described the takeover as an “experiment” that was a “strategic, and at occasions combative, software of recreation idea.”
Builders, miners and safety specialists at the moment are debating whether or not the community’s decentralization is as sturdy as many believed.
What’s a 51% assault?
In a proof-of-work blockchain, miners compete so as to add new blocks of transactions to the chain. If one group controls greater than half of the overall computing energy, they will outpace each different participant.
That stage of management opens the door to a spread of capabilities that may undermine confidence within the community. These embrace chain reorganizations, generally abbreviated to “reorg,” which entails changing beforehand confirmed blocks with new ones. It additionally covers double spends, that means sending the identical token twice,
Arguably probably the most impactful a part of a 51% assault is censoring transactions —stopping some funds from being confirmed — which is especially pertinent within the case of Monero given its concentrate on privateness
These assaults will not be theoretical. Ethereum Traditional was hit a number of occasions in 2020, costing hundreds of thousands. Bitcoin Gold confronted comparable incidents in 2018 and 2020. Smaller tokens like Verge have been focused and destabilized.
Why Monero continues to be in danger
Monero makes use of the RandomX algorithm to discourage mining utilizing software particular built-in circuits (ASICs), encouraging CPU mining as a substitute. This design was meant to maintain the community decentralized. That’s the reason Qubic’s fast rise is so vital. From lower than 2% of Monero’s hashrate in Could, it grew to greater than 25% by late July, and now claims to have crossed the 51% threshold.
Qubic runs a “helpful proof-of-work” system that turns Monero mining rewards into USDT, then makes use of these funds to purchase and burn its personal QUBIC tokens. The mechanism is uncommon, combining a mining technique with a token provide sink. And it has steadily elevated Qubic’s management over Monero’s hashpower.
Qubic simply reached 51% share of Monero. This can be a big feat. They would be the first to control a cryptocurrency with a 51% assault. They intend to orphan all blocks from each different miner, making themselves the one mining entity of Monero. The one technique to mine Monero shall be… pic.twitter.com/rIihj5CtPo
— Caffeinated Person | ꓘ & ױ (@CaffeinatedUser) August 11, 2025
Ledger CTO Charles Guillemet stated that “sustaining this assault is estimated to value $75 million per day,” earlier than including that whereas it’s doubtlessly profitable, “it threatens to destroy confidence within the community virtually in a single day. Different miners are left with no incentive to proceed.”
BitMEX analysis added: “Qubic say the top objective is to takeover all of the block rewards of Monero, which basically means full and sustained egocentric mining. It isn’t clear whether or not they can truly obtain that. If this may be achieved, the worth of the coin could fall.”
It did. Monero’s XMR is at the moment buying and selling at $252, down 6% over the previous 24 hours to compound a 13.5% decline over the previous seven days.
What does this imply for Monero?
Within the weblog publish, Qubic stated the takeover was not about breaking Monero, however about proving that financial incentives and a coordinated mining technique may give a smaller protocol efficient management over a a lot bigger one.
The experiment, Qubic says, was to check whether or not mining assets may very well be profitably diverted from a goal community into one other protocol’s financial loop.
At its peak, Qubic claims its Monero mining was practically thrice extra profitable than conventional Monero mining. A restructuring of its reward system, permitted by its group, boosted payouts to its validators and drew miners away from different Monero swimming pools.
Qubic has reached over 51% of Monero’s hashrate, successfully giving it management of the community.
Qubic selected to not launch the takeover but, proving a robust idea by motion.
However this story isn’t over but. What’s subsequent for Qubic and the way forward for PoW chains?
Article beneath⏬ pic.twitter.com/JqQNqpy95j
— Qubic (@_Qubic_) August 12, 2025
Qubic’s first push for majority management was met with sustained distributed denial-of-service (DDOS) assaults that disrupted peripheral companies for over every week however didn’t take down its core community.
These DDOS assaults continued on Tuesday, Ivancheglo revealed on X, in what he decribes as “Monero Maxis returning the favor.”
Qubic claims it has to this point stopped wanting absolutely taking up consensus, citing issues concerning the potential influence on XMR’s value.
Are different blockchains weak to assault?
Bitcoin’s hashrate is so excessive {that a} 51% assault could be prohibitively costly. However mid-tier proof-of-work cash are extra weak. The price of gaining majority hashpower on Monero, Ethereum Traditional or Bitcoin Gold is way decrease.
Privateness-focused cash face an added problem. Their censorship-resistant nature signifies that if one social gathering controls the community, it undermines the very privateness they’re designed to guard.
