  Monero is a privacy-centric cryptocurrency that makes payments untraceable by
adding decoys to every real input spent in a transaction. Two studies from 2017
found methods to distinguish decoys from real inputs, which enabled
traceability for a majority of transactions. Since then, a number protocol
changes have been introduced, but their effectiveness has not yet been
reassessed. Furthermore, little is known about traceability of Monero
transactions across hard fork chains. We formalize a new method for tracing
Monero transactions, which is based on analyzing currency hard forks. We use
that method to perform a (passive) traceability analysis on data from the
Monero, MoneroV and Monero Original blockchains and find that only a small
amount of inputs are traceable. We then use the results to estimate the
effectiveness of known heuristics for recent transactions and find that they do
not significantly outperform random guessing. Our findings suggest that Monero
is currently mostly immune to known passive attack vectors and resistant to
tracking and tracing methods applied to other cryptocurrencies.
