As the trial of alleged Silk Road drug market creator Ross Ulbricht approaches, the defense has highlighted the mystery of how law enforcement first located the main Silk Road server in an Icelandic data center, despite the computer being hidden by the formidable anonymity software Tor. Was the FBI tipped off to the server's location by the NSA, who used a secret and possibly illegal Tor-cracking technique?

The answer, according to a new filing by the case's prosecution, is far more mundane: The FBI claims to have found the server's location without the NSA's help, simply by fiddling with the Silk Road's login page until it leaked its true location.

In a rebuttal filed Friday to a New York court Friday and accompanied by a letter from the FBI, the prosecution in Ulbricht's case laid out an argument dismissing a series of privacy concerns Ulbricht's lawyers had expressed in a motion submitted to a New York court last month. That earlier motion had accused the government of illegal searches in violation of the Fourth Amendment, including a warrantless search of the Silk Road server, and argued that those privacy violations could render inadmissible virtually all of the prosecution's evidence. The defense motion also demanded that the government explain how it tracked down the Silk Road's server, and reveal whether the NSA had participated in that hunt.

>If the judge accepts the prosecution's explanation, it could represent a major blow to Ulbricht's chances of beating the seven charges against him.

In the latest filing, however, former FBI agent Christopher Tarbell counters Ulbricht's defense by describing just how he and another FBI agent located the Silk Road server in June of last year without any sophisticated intrusion: Instead, he says, they found a misconfiguration in an element of the Silk Road login page, which revealed its internet protocol (IP) address and thus its physical location.

As they typed "miscellaneous" strings of characters into the login page's entry fields, Tarbell writes that they noticed an IP address associated with some data returned by the site didn't match any known Tor "nodes," the computers that bounce information through Tor's anonymity network to obscure its true source. And when they entered that IP address directly into a browser, the Silk Road's CAPTCHA prompt appeared, the garbled-letter image designed to prevent spam bots from entering the site.

"This indicated that the Subject IP Address was the IP address of the SR Server," writes Tarbell in his letter, "and that it was 'leaking' from the SR Server because the computer code underlying the login interface was not properly configured at the time to work on Tor."

That discovery by the FBI, the prosecuting attorneys in Ulbricht's case argue, means that no illegal spying techniques were needed to pinpoint the world's largest anonymous bazaar for narcotics. In fact, they write, the evidence revealing its physical location was left in plain sight.

"Ulbricht conjures up a bogeyman—the National Security Agency ('NSA')—which Ulbricht suspects, without any proof whatsoever, was responsible for locating the Silk Road server, in a manner that he simply assumes somehow violated the Fourth Amendment," the 58-page motion reads. "The facts are not at all what Ulbricht imagines them to be...The Silk Road server was located not by the NSA but by the Federal Bureau of Investigation (“FBI”), using perfectly lawful means."

Ulbricht's defense attorneys didn't immediately respond to a request for comment on the prosecution's brief.

After the initial revelation of the Silk Road server's location in a data center in Reykjavik, Iceland, the filing explains that Reykjavik police accessed and secretly copied the server's data. As agents of a foreign government, the prosecution argues, they weren't required to seek a warrant from any US authority. And the prosecution writes that Ulbricht didn't himself even own the server: He had allegedly rented it through a third-party service, which in turn rented space in the Icelandic data center. The brief goes on to quote the web host's terms of service, which warned that "systems may be monitored for all lawful purposes, including to ensure that use is authorized."

If the judge in Ulbricht's case accepts the prosecution's explanation of that breakthrough in the Silk Road investigation, it could represent a major blow to Ulbricht's chances of beating the seven charges against him, which include conspiracy to traffic in narcotics, money laundering conspiracy, and a "kingpin" charge usually reserved for leaders of drug cartels and mafia organizations. Ulbricht's lawyers have previously outlined a defense against those charges they refer to as the "fruit of the poisonous tree" doctrine, an argument that an initial illegal search taints the rest of the evidence resulting from that violation. On Friday, Ulbricht appeared in court to plead not guilty to new charges that included selling counterfeit IDs and directly trafficking in narcotics rather than merely leading a conspiracy to do so.

>"The Silk Road server was located not by the NSA but by the Federal Bureau of Investigation (“FBI”), using perfectly lawful means."

But the prosecution's motion goes on to request that all of Ulbricht's claims of illegal evidence collection be dismissed. The defense had argued that a surveillance technique known as a pen register applied to Ulbricht's Comcast internet connection without a warrant had also violated his privacy; the prosecution responds that it merely collected metadata rather than the actual content of his communications, and thus didn't require proving probable cause to a judge. The defense's earlier motion argued that when the FBI did get a warrant to seize and search Ulbricht's Samsung laptop, it used an illegal "general" warrant rather than specifying the data it sought. The prosecution claims that it needed to see all data on the machine to establish Ulbricht's alleged identity as the so-called "Dread Pirate Roberts" who had created and managed the Silk Road's billion-dollar drug trade.

"That identification was the fundamental objective of the Government’s investigation," the prosecution's argument reads. "The criminality of the conduct of the Silk Road user 'Dread Pirate Roberts' was manifest throughout the operation of Silk Road. The mystery was his true identity. And the Government sought to analyze Ulbricht’s writings and his travel patterns in order to confirm that 'Dread Pirate Roberts' was indeed Ulbricht."

In last month's motion, Ulbricht's defense hadn't only addressed issues of privacy and potentially illegal searches. It had also requested that the government strike from its indictment accusations that Ulbricht paid for the murder of six people. Ulbricht's defense and his family have protested that grisly element of the indictment, which has yet to result in any actual criminal charges, has been used to scare off support for the 30-year-old despite a lack of necessary evidence to press those charges of violence.

But the prosecution counters that the uncharged murder accusations show Ulbricht's character and motivations. "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," the prosecution writes.

Finally, the prosecution dismisses a request from Ulbricht's defense for more information on a series of facts in the case, including all agencies and contractors involved in the Silk Road investigation, and the names of all software tools used to scan for potential vulnerabilities in its infrastructure.

"There is therefore no basis—especially at this late juncture, six months after discovery was originally produced—for Ulbricht to go on a 'blind and broad fishing expedition' for proof of some darker, alternative storyline, somehow involving violations of his Fourth Amendment rights, when there isn’t a shred of evidence that any such violations actually happened," the motion concludes.

Read the full filing from the prosecution in the Silk Road case below, and at bottom, the letter from Tarbell explaining how the FBI discovered the location of the Silk Road site.

Silk Road Prosecution 4th Amendment Rebuttall

FBI Explanation of Silk Road vulnerability