In November 2014, law enforcement and prosecutors in Europe and the US launched Operation Onymous, an international operation aimed at taking down online illegal markets and arresting vendors and administrators of such markets. The operation was coordinated by Europol’s European Cybercrime Centre (EC3), Eurojust, the FBI, and the U.S. Immigration and Customs Enforcement’s (ICE) Homeland Security Investigations (HSI). The operation culminated in the arrest of 17 individuals and the seizure of Bitcoins amounting to USD 1 million, drugs, gold and silver.

Among the marketplaces brought down were Silk Road 2.0, an online black market and used to sell drugs and other illegal items. In 2013, the FBI shut down its predecessor, Silk Road 1.0 and arrested its founder Ross Ulbricht, who was convicted in February 2015 in the US. Silk Road 2.0 was launched in November 2013 after the shutdown of its previous version. On 5 November 2015, the alleged administrator of Silk Road 2.0, Blake Benthall, was arrested by the FBI in San Francisco. According to the FBI, as of September 2014, Silk Road 2.0 had sales of at least approximately $8 million per month and approximately 150,000 active users. As a part of the investigation, an undercover HIS agent infiltrated in the administration of Silk Road 2.0 and obtained access to restricted information.

Silk Road 2.0 and other online marketplaces shut down as part of this investigation were operated as TOR hidden services. The TOR (The Onion Router) network is a worldwide network that allows users to establish anonymous communication. A TOR hidden service does not reveal the IP address of the server used . TOR is used for both illicit and licit purposes, with the latter including members of the military as well as activists and journalists evading censorship.

Most transactions on the shuttered marketplaces were carried out in Bitcoins. Bitcoin is a decentralized cryptocurrency, i.e. there is no centralized authority and Bitcoin transactions are processed and validated by a peer-to-peer network. Bitcoin users are anonymity but all its transactions are stored in a public ledger. Information on Bitcoin users can be obtained from exchanges – institutions converting Bitcoin into other currencies or vice versa – and other points of intersection with the regulated financial system.