When the first Silk Road and its alleged operator, Ross William Ulbricht, were taken down by the US government just over a year ago , it took some technical mojo to track down the server and its operator. That apparently wasn’t the case with Ulbricht’s successor. According to the US Attorney’s office for the Southern District of New York , Silk Road 2.0 was the victim of some old-fashioned social engineering of the most damaging kind. An undercover federal agent was able to join the site's administration team and gather the intelligence that led to the arrest of Blake Benthall—the alleged operator of the Silk Road successor site who went by the name “Defcon.”

The first Silk Road site, like version 2.0, operated as a “hidden service” on the Tor .onion anonymized network. The FBI claimed that it was able to exploit a flaw in a “captcha” feature of the concealed website to obtain Silk Road 1.0's actual IP address and track the server to a data center in Iceland. Ulbricht’s attorneys called the explanation “implausible,” accusing the FBI of unlawfully hacking the server.

However, in its investigation of Silk Road 2.0, the government took a different technical tack. In a statement issued by the US Attorney’s Office about the arrest, a spokesperson said, ”During the Government’s investigation, which was conducted jointly by the FBI and [Homeland Security Investigations], an HSI agent acting in an undercover capacity (the “HSI-UC”) successfully infiltrated the support staff involved in the administration of the Silk Road 2.0 website and was given access to private, restricted areas of the site reserved for Benthall and his administrative staff. By doing so, the HSI-UC was able to interact directly with Benthall throughout his operation of the website.”

According to the criminal complaint filed in US Court today, the HSI undercover investigator got in on the ground floor with Silk Road's second incarnation. "DPR2," the original operator of the new site, created a forum to discuss launching a replacement site on a hidden site on the Tor network on October 7, 2013—less than a week after the original site was seized. The undercover investigator was invited to join the forum, and the next day was granted forum moderator privileges; by January 2014, the investigator was a paid staff member, receiving 16 payments in Bitcoins totalling about $32,189 based on current exchange rates.

With that level of authorized access—and with communications directly with Benthall—the FBI and HSI would have been able to gather evidence directly from the site’s server and then use other measures to de-anonymize the individuals associated with it. It’s possible that the investigators may have allowed the site to continue to operate for a period of time to act as a “honeypot” to gain further information about transactions being passed through the marketplace. According to the criminal complaint, "foreign law enforcement authorities" imaged the Silk Road 2.0 server on May 30—which means the site was allowed to continue to operate for five more months while the FBI, HSI, and partner law enforcement organizations gathered data.

That's likely how Irish authorities got information required to stage a drug raid yesterday in Dublin, seizing approximately $200,000 worth of LSD, Ecstasy, and other drugs as well as $18 million in bitcoin. The Irish Examiner reports the raid was the "result of an international drug trafficking investigation into the sale and supply of controlled drugs on an encrypted layer of the internet known as 'the Darknet'." The operation is part of a broader FBI/Europol operation called 'Onymous," the Examiner reports—"an international day of action to disrupt global activity on the Darknet and remove certain websites and forums is to conclude within the next 24 hours."

UPDATE, 1:50pm CT: This report has been updated with additional information after the criminal complaint court documents were unsealed. Ars will continue to monitor the situation and update this report if new information becomes available.