If the drama in the crypto space is never short of stories, this time, the protagonist has become Monero.
This was not a sudden attack but a power showdown that was announced a month in advance— the attacking party even announced that they would 'challenge the Monero network from August 2 to August 31.' Their goal was aimed at a rare achievement in the blockchain world: controlling 51% of the hash rate of a privacy coin network valued at over $5 billion.
And today, the attackers claim to have achieved that goal.
This is a premeditated attack.
We all know that in a blockchain network, all transactions must be verified by miners, a process known as 'mining.' The computational power of miners is called hash rate; the higher the hash rate, the greater the chance of mining new blocks and receiving rewards.
The same goes for Monero.
However, compared to other coins, Monero has a design that prevents large mining pools from behaving maliciously— it does not support dedicated mining machines (ASICs) and can only be mined using ordinary computer CPUs or GPUs. The intention behind this rule is to prevent all miners from gathering in one large mining pool, making it theoretically possible for anyone to participate in mining with their own computer, leading to a more fair and decentralized network.
However, this mechanism also has an idealized way to be attacked, which is to rent or mobilize a large number of ordinary servers (such as cloud computing resources, idle PCs, miners' computers) in a short period of time. And this is precisely how the attackers executed this.
Now let's take a look at this premeditated attacker, called Qubic.
The initiator of this action is Qubic, an independent blockchain project not originally created to attack Monero. It is led by Sergey Ivancheglo (alias Come-From-Beyond), co-founder of IOTA and a senior crypto developer, using a 'Useful Proof of Work' (UPoW) mechanism that allows miners' hash power to be used not only to solve mathematical problems but also to train its artificial intelligence system 'Aigarth', achieving two goals at once.
So why did it become associated with Monero and launch a 'war' against it?
In fact, this is an 'economic demonstration' of Qubic showcasing its UPoW model capabilities. Starting in May 2025, it has successfully attracted a large number of miners to join by using its network hash rate for CPU mining of Monero, simultaneously earning rewards in both Monero and $QUBIC tokens. The Monero mined will be sold for stablecoins, which will then be used to repurchase and burn Qubic coins, creating a self-reinforcing economic loop.
After Qubic announced its intention to 'challenge' the Monero network from August 2 to August 31, some members of the Monero community began to monitor the chain's situation around the clock. Someone mentioned on Reddit that they would watch every block, especially paying attention to the emergence of 'orphan blocks.' Initially, everything was normal, but one day at dawn, they noticed a chain reorganization occurred. Normally, chain reorganizations are not uncommon in the Monero network; for example, when two miners simultaneously mine blocks, the system will choose one and discard the other. However, the timing of this was suspicious, seemingly related to Qubic testing the insertion of alternative blocks and forking the blockchain. Although that alternative block was ultimately rejected, it indicates that Qubic was attempting to take action.
Monero block status
Monitors also found that Monero should generate a block every two minutes, but the block generation speed has recently accelerated noticeably, suggesting that the network might be detecting signs of potential attack. This made him certain that Qubic was indeed carrying out some form of interference. Another participant pointed out that the only orphan block that appeared was 12 hours before Qubic publicly claimed it would launch an attack.
In terms of hash rate data, the community also observed that Qubic stopped reporting its hash rate to public mining pool statistics websites in early August, making it impossible for the outside world to see their real mining capability directly. Some speculate that this may be to hide peak hash rates, create a lack of transparency, while displaying more favorable numbers on their own controlled website. Members of the Monero core team analyze that their hash rate is not constant but switches regularly between peaks and troughs, making this 'switching' mode more threatening than stable mining.
The result of this premeditated attack by Qubic to 'flex its muscles' was that during May to July, Qubic occupied nearly 40% of the Monero network's hash rate. By August, Qubic claimed to have reached 52.72%, directly crossing the 51% 'control threshold'—this means it technically could reorganize chains, conduct double-spending attacks, or censor transactions. Qubic claimed this was to simulate potential attacks that the Monero network might face, to discover security weaknesses early.
Is it true that Qubic is just bluffing?
So did Qubic really succeed in executing a 51% attack? Many still hold a skeptical attitude towards this, believing it was merely a deliberately deceptive marketing ploy.
@VictorMoneroXMR raised doubts with the following screenshot. When the total hash rate of other Monero mining pools showed 4.41 GH/s and the total network hash rate showed 5.35 GH/s, Qubic's data dashboard showed that it had 2.45 GH/s under the same total network hash rate, which clearly does not match, and it is possible that Qubic's data dashboard did not include its own hash rate in the total network hash rate. If we correct based on this assumption, Qubic's hash rate actually accounts for only about 30% of the total hash rate.
Apart from the data doubts, the most direct on-chain evidence currently is that Monero has suffered six consecutive block reorganizations, but this does not definitively prove that Qubic has the capability to launch a 51% attack.
This point is also corroborated by real-time monitoring posts in the Monero Reddit community regarding blocks.
During the entire Qubic challenge period, the community did not see a sustained, significant increase in orphan blocks or chain reorganizations, with only one suspected reorg, and the alternative block was rejected. Core developers and the community observed that Qubic had come close to or even slightly exceeded 50% of the hash rate at certain times (Qubic claimed to have reached 52.72%). Even if it exceeds 51% for a short time, if only for a few minutes or a few blocks, it may not be able to mount an effective attack.
That is to say, there is currently no evidence showing that they maintained a stable 51% or more for a long enough time to launch a successful attack.
Currently, the consensus in the Monero community is that Qubic may have briefly exceeded 51%, but did not execute an effective attack, more like a demonstration of hash rate and psychological warfare. The attacking party may display exaggerated screenshots of their share on their website to create the impression that they have controlled the network.
Spending $75 million to earn $100,000 in a losing trade?
The cost of Qubic's attack has also sparked extensive discussion on social media.
The analysis within the Monero community generally believes that maintaining the current hash rate controlled by Qubic is extremely costly. Based on the current network difficulty, the daily block rewards of the entire Monero network are valued at approximately $150,000. If the attackers want to maintain over 50% of the total network hash rate continuously, it means they need to produce blocks equivalent to half or more of the entire network's output daily, which entails staggering costs for hardware, electricity, and operation.
According to calculations by Yu Xian, founder of the security company SlowMist, the cost of such an attack could be as high as $75 million per day, a figure that is almost impossible to recoup through mere speculative mining.
Due to the exorbitant nature of this figure, let's analyze it from other perspectives. First, look at Crypto51, a website specifically designed to estimate the cost of executing 51% attacks on different PoW coins. For some mainstream or small to medium market cap coins, it provides cost references for hourly hash rate leasing, such as: Ethereum Classic (market cap around several hundred million dollars): about $11,563 per hour; Litecoin: about $131,413 per hour.
Although Crypto51 does not provide specific data for Monero, it can be seen that even for medium-sized PoW networks, the attack costs are usually far below the tens of millions of dollars per day level.
Based on discussions on Reddit, a community friend attempted to estimate the attack cost for CPU PoW (such as Monero) as follows: assuming the use of an AMD Threadripper 3990X (performance around 64 KH/s), to achieve 51% of the total network would require about 44,302 of these CPU machines. The purchase cost alone would be roughly $220 million (44,302 × $5,000). Including other hardware costs, venue rentals, and electricity costs, an additional tens of millions of dollars would be needed. Electricity costs are estimated at about $100,000 per day.
So how much profit can Qubic make from a $75 million daily attack cost?
According to Monero's current tail emission rules, the block time is about 2 minutes, and the reward for each block is fixed at 0.6 XMR. If Qubic controls over 51% of the hash rate, it means they can mine all the Monero blocks produced daily, which is about 432 XMR.
At the time of writing this article, the price of Monero was approximately $246. Based on the current price of Monero, if Qubic monopolizes all Monero output for one day, it could only profit about $106,000.
According to Qubic's official 'Epoch 172 Report,' Qubic distributes the Monero it mines in a 50%-50% ratio, with half used for repurchasing and burning $QUBIC and the other half used for miner incentives. However, miners' rewards are still paid in $QUBIC.
In other words, the $QUBIC, with a market capitalization of less than $300 million, has the ability to produce Monero, which has a market cap of nearly $4.6 billion. Theoretically, they could go all out and destroy $53,000 worth of $QUBIC in a day and $1.509 million worth of $QUBIC in a month, which is truly insane.
Monero's counterattack, an ongoing struggle.
Therefore, the outside world generally believes that Qubic's motivation is not just to mine Monero for profit directly, but to support a 'hash rate + token' combined economic model: Qubic does not pay miners directly with fiat currency but uses its own token $QUBIC as a reward and artificially maintains the secondary market price of the token—once the price stabilizes or even rises, it can exchange a relatively low token issuance cost for massive real hash rate support. The core of this approach is that the rewards miners earn from mining Monero in the Qubic pool will be exchanged for Qubic tokens; if the token price remains high, the nominal profits for miners will be considerable, naturally attracting them.
In terms of profit models, Qubic itself does not necessarily rely on Monero's block rewards to make money, but instead uses this event to generate hype for its token, increase transaction volume and prices, and thereby attract more speculative buying.
As long as the market value and liquidity of Qubic Coin are maintained at a level sufficient to pay miners, this large-scale hash rate occupation can continue. However, this model is built on a highly fragile foundation of confidence: if miners feel that the price of Qubic Coin is difficult to maintain, they will collectively sell to return to more stable assets, which will trigger a price collapse and initiate a 'first-come, first-served' stampede.
This is a blatant and domineering siphoning of hash rate, naturally provoking strong dissatisfaction and retaliation from the Monero community.
Interestingly, during the process of Qubic attacking Monero, it also suffered anonymous attacks.
According to Qubic founder Sergey Ivancheglo (alias Come-From-Beyond), their mining pool experienced a DDoS attack (Distributed Denial of Service) during this phase. Qubic provided data showing that its mining pool's hash rate dropped from about 2.6 GH/s to 0.8 GH/s, a decline of over 70%. Therefore, he believes that someone deliberately interfered with their hash rate operations through a network attack.
The attacking party, Qubic founder Sergey Ivancheglo, stated that he was also attacked.
During the accusations, Ivancheglo even specifically named Sergei Chernykh (nickname sech1), the main developer of Monero mining software XMRig, as a potential instigator behind the scenes. However, sech1 immediately responded, clearly denying any involvement in illegal attacks: 'I am not the only one in the Monero community unhappy with Qubic's actions. But I will never resort to illegal means like DDoS. Others might.'
The main developer of Monero mining software XMRig stated, 'I am not the only one in the Monero community unhappy with Qubic's actions.'
At the same time, it seems that the Monero community is also discussing that all Monero enthusiasts should organize and completely eliminate Qubic:
'We need a #ShortQubic movement; if they want to provoke us, we can only counterattack. After all, the Monero community is larger.' 'Where to short Qubic? Why don't we collectively short Qubic Coin, or even leverage? That would completely kill the miners' enthusiasm.'
The Monero community discusses how to counterattack.
Interestingly, some members of the Monero community pointed out that there might also be ideological reasons behind Qubic's attack on Monero.
The Qubic website shows that the team has many members, but most use pseudonyms, with only two using real names: one is the aforementioned Qubic founder Sergey Ivancheglo, and the other is Qubic scientist David Vivancos, who has been advocating for human-machine collaboration. David Vivancos is described as a 'technocrat' who believes in a model of societal management driven by technical experts and data. This ideology has been criticized as being contrary to Monero's pursuit of decentralization, privacy, and community autonomy, and even carries a dystopian tint.
This battle has not ended; the smoke of psychological warfare is still lingering. Next, will the Monero community counter Qubic with technology, finance, or public opinion? And how long can Qubic's 'hash rate siphon' last? Rhythm BlockBeats will continue to monitor this.
