Inside Qubic's Selfish Mining Campaign on Monero: Evidence, Tactics, and Limits

TL;DR

This paper investigates Qubic's selfish mining attack on Monero in 2025, combining measurements and models to assess its effectiveness, revealing it is not profitable under average conditions but can be intermittently profitable.

Contribution

It provides a detailed analysis of Qubic's attack using real measurements and models, highlighting the attack's limits and the importance of time-varying hashrate considerations.

Findings

Qubic's average hashrate share rises to 23-34% during attack intervals

Models predict revenues below honest mining at inferred parameters

Attack can be profitable intermittently despite not having majority control

Abstract

We analyze Qubic's publicly claimed selfish mining attack against Monero in 2025. By combining measurements from Monero nodes, the Qubic pool API, and Qubic-network observations, we reconstruct Qubic-attributed blocks and effective hashrate and identify ten intervals consistent with block withholding and strategic release. During these intervals, Qubic's average hashrate share rises to 23--34\%, yet we never observe sustained majority control. We evaluate the attack using the classical selfish mining model and a Markov-chain variant that captures Qubic's conservative release policy. At the inferred parameters, both models predict revenues below honest mining, and our measurements largely confirm this while showing systematic deviations. We attribute the gap to hashrate variability, coarse-grained interval detection, and operational frictions under community countermeasures. We further argue that selfish mining should be analyzed under time-varying hashrate. Even when the average hashrate stays below the static break-even point, an attacker can still run a profitable selfish-mining operation by operating it intermittently.