The FBI easily found the main server of the now-defunct Silk Road online drug-selling site, and didn't need the National Security's help, federal prosecutors said in a Friday court filing.

The underground drug website, which was shuttered last year as part of a federal raid, was only accessible through the anonymizing tool Tor. The government alleges that Ross Ulbricht, as Dread Pirate Roberts, "reaped commissions worth tens of millions of dollars” through his role as the site's leader. Trial is set for later this year.

The authorities said Friday that the FBI figured out the server's IP address through a misconfiguration in the site's login window. They said that a US warrant wasn't required to search the Icelandic server because "warrants are not required for searches by foreign authorities of property overseas."

According to Serrin Turner, assistant US attorney in New York:

Having failed in his prior motion to dismiss all of the Government’s charges, Ulbricht now moves this Court to suppress virtually all of the Government’s evidence, on the ground that it was supposedly obtained in violation of the Fourth Amendment. Ulbricht offers no evidence of any governmental misconduct to support this sweeping claim. Instead, 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.

Turner wrote [PDF] that the server's IP address was "leaking" from the site "due to an apparent misconfiguration of the user login interface by the site administrator—i.e. Ulbricht."

The government said that the FBI learned of IP addresses of additional servers after examining code on the main server.

The image of the main server was taken "covertly" by the Reykjavik Metropolitan Police, the authorities said. The US said they followed legal process "required under Icelandic law to search the server."

Ulbricht has pleaded not guilty.

The accused Silk Road mastermind faces a lengthy prison sentenced if convicted of narcotics, hacking and money-laundering charges. He is also accused of "continuing a criminal enterprise."

The court's legal filing came a day after two prominent Bitcoin supporters pleaded guilty to federal charges of facilitating drug trafficking on the Silk Road site.