$6B Privacy Coin Monero Was Just Hijacked for $100K/Day – Here’s Why That’s Terrifying

Monero, the $6 billion privacy coin long touted as one of crypto’s most censorship-resistant networks, has suffered a major setback.

Key Takeaways:

• Qubic claims it gained 51% control of Monero’s hashrate after a month-long campaign.
• The takeover coincided with a six-block chain reorganization that replaced 60 blocks.
• Monero developers dispute that a full 51% attack occurred, while some security experts say the attempt appears to have succeeded.

A single mining entity, the Layer-1 blockchain Qubic, claims it seized 51% of Monero’s hashrate, a level of control that in theory could rewrite the chain, double-spend transactions, or censor activity — all for an estimated cost of just $100,000 per day.

The revelation came from a recent post by X user Pix, who summarized the incident as a textbook case of “too big to attack” being proven wrong.

In a blog post earlier this week, Qubic said the takeover was the result of a month-long campaign that culminated on Monday, coinciding with a six-block-deep chain reorganization that replaced 60 previously valid blocks. The move briefly pushed Monero’s price down around 7%.

A 51% attack occurs when one party controls the majority of a blockchain’s mining power or stake, allowing them to alter the chain’s history or block transactions.

In Monero’s case, Qubic had incentivized CPU miners to direct their power toward XMR instead of other coins, promising better rewards through its network.

Founder Sergey Ivancheglo admitted the strategy was designed to monopolize Monero’s mining, eventually rejecting blocks from rival pools.

While Qubic says the event demonstrates it achieved full network control, Monero developers have pushed back.

Luke Parker, lead developer at SeraiDEX, argued that the six-block reorganization doesn’t definitively prove a successful 51% attack, only that “an adversary with a high amount of hash got lucky.”

A 6 re-org does not mean a '51% attack' was successful. In that case, we'd see unbounded-depth re-orgs/no blocks mined by any other mining pool (assuming the adversary censors other mining pools, as this one does).

It does mean an adversary with a high amount of hash got lucky.

Others aren’t so dismissive. Zhong Chenming, co-founder of cybersecurity firm SlowMist, said the attack “seems to have succeeded,” warning that Qubic’s pool could now, in theory, rewrite the blockchain and censor any transaction.

The confrontation began in late June, when Qubic announced it was redirecting its proof-of-work model, typically used for AI-related tasks, toward Monero mining.

The mined XMR would fund Qubic token buybacks and burns, creating a direct economic incentive to overpower the network.

Monero’s community quickly mobilized. In late July, members allegedly launched a distributed denial-of-service (DDoS) attack against Qubic’s mining pool, briefly dropping its hashrate from 2.6 gigahashes per second to 0.8 GH/s.

#Qubic pool hashrate peaked 2.6 GH/s before #Monero DDoS attacks knocked it down to 0.8 GH/s by making 2/3 of miners disconnect.

However, by August, Qubic’s position appeared secure enough to trigger the six-block reorg.

“In a move that has rewritten the rules of blockchain competition, a $300 million market cap AI protocol has successfully asserted its dominance over a $6 billion market cap privacy giant,” Qubic wrote.

For now, Qubic says it has “paused” the takeover, claiming it chose not to push the attack further.

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