European Union law enforcement agency Europol has for the first time released a cybercrime report examining the growing role of zcash, monero and ether on the darknet.

In the 2017 Internet Organised Crime Threat Assessment (IOCTA), Europol states that, although bitcoin is still the preferred currency in cybercrime, the landscape is beginning to evolve, with "monero, ethereum and zcash … gaining popularity within the digital underground."

The research document analyzes the differing desirability of these cryptocurrencies for cybercriminals, and concludes that monero is increasingly popular due to the "additional security and privacy features it offers."

The document explains:

"Transactions cannot be attributed to any particular user/ address, all coins used in a transaction are 'hidden' by default, and transaction histories are kept private."

Europol also mentions the cryptocurrencies' popularity on darknet marketplaces, and decribes the first known case, earlier this year, of a monero-focused ransomware named Kirk.

Discussing ethereum's ether token, the assessment restates Europol's earlier concerns that smart contracts could be used to formalize payments between crime service providers. Further, it documents a case of a decentralized darknet market planned to operate on the ethereum blockchain.

The document goes on to say that zcash "has yet to feature in any reported law enforcement investigations." However, due to its privacy features, which involves "obscuring both the transaction recipient and transaction amount," darknet marketplaces are interested in the currency.

Although since disbanded, the largest darknet market AlphaBay added monero and ethereum as payment options in the year prior to its closure, and had plans to implement zcash.

Europol shutdown AlphaBay earlier this year as part of an internationally coordinated darknet crackdown.

An investigative document stated at the time that authorities had seized large quantities of bitcoin, ethereum, zcash and "an unknown amount of monero" from the site administrator. Monero enthusiasts celebrated the statement on social media as proof of the resilience of the currency.

Coindesk