By Sudip Kar-Gupta and Raphael Satter

BRUSSELS (Reuters) – International authorities have cracked down on the cryptocurrency platform ChipMixer, alleging it helped obscure the digital money trail for online drug dealers, Russian military hackers and North Korean cybercriminals, Europe’s Europol police agency and the U.S. Department of Justice said on Wednesday.

The site – which authorities say laundered more than $3 billion worth of cryptocurrency – was offline on Wednesday, replaced by a banner which read, “THIS WEBSITE HAS BEEN SEIZED” and displaying the logos of German, American, Swiss and Polish law enforcement organizations.

The Justice Department said it had charged Vietnamese national Minh Quoc Nguyen, 49, with money laundering and identity theft in connection with the platform’s operation. In its indictment, the department claimed that Nguyen openly flouted financial regulations and at one point told users of a Bitcoin forum that “‘Money laundering’ is a crime made-up by governments that spy on their citizens.”

In an email, the Justice Department said Nguyen was not in custody. Reuters was not immediately able to determine his current whereabouts; attempts to reach him by email were not immediately successful. A message sent to ChipMixer’s publicly posted email address was not immediately returned.

ChipMixer, an unlicensed cryptocurrency mixer set up in mid-2017, specialised in mixing or cutting trails related to virtual currency assets, authorities said. Europol described it as “one of the darkweb’s largest cryptocurrency laundromats” and said that more than 40 million euros ($42.2 million) worth of cryptocurrency had been seized.

Digital currency tracking service Elliptic said ChipMixer had been used to launder over $844 million in Bitcoin that it tied directly to illicit activity – including at least $666 million from cryptocurrency thefts.

Elliptic said in a blog post that ChipMixer was one of several mixers used to launder proceeds of hacks perpetrated by the Lazarus Group, a hacking gang that cybersecurity specialists and Western countries allege to be operated out of North Korea.

The Justice Department said the Russia’s military intelligence service – best known under its old acronym, the GRU – had also used the service to purchase infrastructure for hacking operations.

Because blockchain transactions are publicly visible, cybercriminals often use mixers to obscure the trail of ill-gotten digital currencies and other such services that have been subject to law enforcement seizure in the past.

In May 2019, for example, Europol announced the seizure of Bestmixer.io, a similar site.

($1 = 0.9488 euros)