The Federal Bureau of Investigation (FBI) released information on Friday detailing how it allegedly discovered Silk Road and linked Ross Ulbricht to the illicit website.

The 58-page filing, submitted to the US District Southern Court of New York, offers a lengthy rebuttal to recent assertions by Ulbricht. He claimed the methods used by federal officers during the investigation of Silk Road were unlawful and that, as such, the information recovered through this process should not be admissible in court.

Penned by FBI agent Christopher Tarbell, the document offered a four-point critique of the motion Ulbricht and his defense team first filed in August, though the overall tone was crafted as to suggest that the FBI is dismissive of any claims levelled against its work by Ulbricht.

Tarbell wrote:

“[Ulbricht’s] various claims are bereft of any support in the law. […] Instead, they amount to a pointless fishing expedition aimed at vindicating his misguided conjecture about the NSA being the shadowy hand behind the government’s investigation.”

The filing goes on to suggest how the government was able to identify servers used to operate the Silk Road website, along with the various steps that federal officials took to connect this information to ‘Dread Pirate Roberts’, the alias allegedly used by Ulbricht to operate the website. It also argues all Ulbricht’s claims that illegal evidence was used in the case should be dismissed.

Notably, the filing has not been without its critics, who allege inconsistencies with the government’s official version of the events.

Lawful means

Central to the FBI’s rebuttal was that agents noticed that the server’s Internet protocol (IP) address was ‘leaking’ information from the Silk Road website due to an “apparent misconfiguration of the user login interface by the site administrator”.

Exploiting this error, the FBI says, it was able to reveal certain IP addresses that were not protected by the Tor network, and could thus trace the addresses to physical locations.

Contrary to Ulbricht’s claims, the US government argues it:

• Did not need to release information about how it found the Silk Road website when it originally obtained its search warrant
• Lawfully used PEN registers during the investigation to collect routing data, as they do not require a warrant
• Was approved to search Ulbricht’s email and Facebook for evidence of wrongdoing after establishing probable cause
• Was not required to obtain a warrant to search the Silk Road server because the investigation was carried out by foreign authorities

Iceland’s intervention

The FBI further addressed the role of Icelandic law enforcement officials in the investigation, who Ulbricht and his legal team have alleged were used strategically to bypass the Fourth Amendment protections Ulbricht is afforded as a US citizen.

Offering a rebuttal of this stance, the filing argues that US authorities approached their peers in Iceland because the Silk Road server was located in this jurisdiction.

However, the FBI also indicated that any search by Icelandic law enforcement officials would not involve Fourth Amendment requirements, as this right does not apply outside the US.

“It is well established that the Fourth Amendment’s warrant requirement does not apply overseas – even to searches conducted directly by US law enforcement agents of property belonging to a US citizen,” the filing reads.

Pen registers

The FBI went on to reject the notion that it used a surveillance technique known as a pen register to track Ulbricht’s location. Rather, the filing suggests such tools were used to monitor Ulbricht’s Internet activity, and that these logs were compared to records of the Dread Pirate Roberts’ online activity to identify Ulbricht as the site’s operator.

Still, the government moved broadly to reject the idea that Ulbricht had a right to privacy in this case at all given the need for law enforcement officials to take action against Silk Road.

The report stated:

“In any event, whatever expectation of privacy Ulbricht did have in the SR server, it was plainly outweighed by the government’s legitimate need to search its contents. The government had ample evidence, easily enough to establish probable cause, that the SR server was hosting the Silk Road website.”

The filing added: “Under the circumstances, searching the server was more than reasonable. It was a law enforcement imperative that would have been a gross dereliction of duty for the government not to pursue.”

Murder-for-hire allegations are relevant

Ross Ulbricht’s defense was also handed another potential blow in the prosecution’s insistence that the murder-for-hire allegations are relevant to the case.

The filing suggests the allegations provide valuable context for Ulbricht’s state of mind at the time he was allegedly operating Silk Road, and as such, should be admissible in court.

Tarbell wrote:

“The use of violence and threatened violence to protect one’s drug empire are relevant to proving the intentional operation of a narcotics conspiracy, and such conduct may be alleged as overt acts in furtherance of such a charge.”

Notably, Ulbricht was not indicted on murder-for-hire charges in New York, though one such charge was filed in a Maryland court.

Doubts cast on FBI explanation

Despite the strong and persuasive language evoked by the FBI, critics of the filing and the plausibility of the government’s version of events have emerged.

For example, Australian blogger and hacker Nik Cubrilovic first detailed his criticism of the filing on 7th September, noting a series of issues with the reasoning listed in the report.

Cubrilovic alleged that while Tor configurations can leak information, the FBI cited an incorrect page in an attempt to bolster this claim. Further, he asserts the process detailed by the FBI is vague, adding that anybody with knowledge of Tor and hidden services would not be able to read or replicate the process FBI agents said they completed.

CAPTCHA concerns

Speaking to Wired, privacy researcher Runa Sandvik suggested the details regarding how the FBI allegedly exploited a Silk Road CAPTCHA page to establish the location of the Silk Road server were problematic.

Sandvik indicated she believes the CAPTCHA was hosted on the same server as Silk Road, meaning it would have been only accessible through the Tor network. Such a finding by the FBI, Sandvik reasons, would represent a flaw with Tor and not Silk Road’s site architecture.

Cubrilovic came to a similar conclusion in his blog post, speculating that operators of the site would have likely noticed such an error. He told Wired:

“The way they’re trying to make a jury or a judge believe it happened just doesn’t make sense technically.”

The development marks the latest update in the ongoing prosecution of Ross Ulbricht. The trial is set to begin this November.

At press time, Ulbricht’s attorney Joshua Dratel told CoinDesk that they were still evaluating the newest case filing, and that a formal response would be forthcoming.

FBI image and server image via Shutterstock