In August 2025, Monero experienced one of the most significant security incidents in its history. Blockchain security firm Halborn reported that a mining pool linked to Qubic executed a six-block deep reorganization on Monero’s chain, orphaning around 60 blocks. Many in the industry described this as a successful 51% attack.
Qubic, led by IOTA co-founder Sergey Ivancheglo, had grown its share of Monero’s hashrate from under 2% in May to more than 25% by late July, eventually crossing the critical 51% threshold. The pool’s economic model further amplified its influence: mined XMR was converted to USDT to buy and burn QUBIC tokens, offering miners significantly higher returns and drawing even more hashpower into its orbit.
Reactions within the crypto community were divided. Some experts, such as Ledger CTO Charles Guillemet, warned that this represented a real-time 51% attack, giving Qubic the ability to rewrite the chain, censor transactions, and potentially double-spend. Others argued that the incident might have been an unusually lucky run by a powerful pool rather than a sustained takeover. Regardless, the event caused immediate market consequences – Monero’s price dropped sharply, and some exchanges temporarily halted withdrawals.
Why a 51% Attack on Kaspa Is Far More Difficult
While the Monero incident exposed the risks faced by traditional proof-of-work blockchains, Kaspa’s architecture is built to make such attacks significantly less practical. Several design choices work together to create a more resilient network.
1. BlockDAG and GHOSTDAG Consensus
Kaspa uses a blockDAG structure via the GHOSTDAG protocol, which allows multiple parallel blocks to coexist instead of orphaning them. This reduces the advantage an attacker can gain by mining secretly, since honest blocks are not discarded and still contribute to consensus.
2. High Block Rate and Inclusive Mining
With a block rate of ten per second (and plans for much higher throughput in the future), Kaspa ensures that the network quickly incorporates all blocks. In traditional chains, attackers benefit when honest blocks are orphaned, but Kaspa’s inclusive approach removes that leverage.
3. Economic Security Through ASIC Scarcity
Kaspa’s network is secured by specialized ASIC mining hardware, which is costly to produce and in limited supply. Acquiring enough machines to mount a 51% attack would require significant upfront capital, long lead times, and coordination to source hardware from a market already dominated by existing miners. Unlike GPU-mined coins, where hashpower can be rented or quickly redirected, Kaspa’s ASIC dependency makes it a great deal more expensive – and logistically challenging for an attacker to gain majority control.
4. Secure Pruning with UTXO Commitments
Kaspa uses cryptographic UTXO commitments to enable secure pruning, meaning nodes only need to keep a few days of full history. This drastically narrows the window in which a deep reorganization could occur, requiring an attacker to act quickly and visibly, increasing the chance of detection and counteraction.
The Bottom Line
Monero’s 51% reorganization demonstrates that even established proof-of-work networks can be vulnerable when mining incentives align in the wrong way. Kaspa’s combination of blockDAG consensus, high throughput, ASIC-based mining security, and pruning technology makes a similar attack exponentially harder to carry out.
While no blockchain can claim absolute immunity, Kaspa’s design significantly raises the cost and complexity of a majority attack, turning what happened to Monero from a worrying possibility into a near-impractical scenario.
