The FBI closed down notorious narcotics distribution site Silk Road using a hole in its Captcha prompt.
The site was pulled temporarily in October last year despite supposedly being impossible to take down after the US security organisation managed to find the company's hidden servers.
FBI agent Christopher Tarbell explained: "The IP address leak we discovered came from the Silk Road user login interface. Upon examining the individual packets of data being sent back from the website, we noticed that the headers of some of the packets reflected a certain IP address not associated with any known Tor node as the source of the packets."
When the address was typed into a normal browser, it brought up the Captcha login prompt, revealing it was the IP address of Silk Road's server.
The FBI then contacted authorities in Iceland, where the servers were located, demanding access to routing information and images of the server contents to examine.
The organisation found "databases of vendor postings, transaction records, private messages between users, and other data reflecting user activity" on the server images that proved they were being used to host Silk Road.
It then discovered backups of the servers being used in Pennsylvania that were also searched and seized in October, causing the site to temporarily close.
The notes were filed in documents prepared to counter Silk Road founder Ross Ulbricht's claims that his Fourth Amendment Rights had been violated when he was searched and the website's servers were brought down as part of the investigation into multiple drug and ID fraud charges.
According to Forbes, law dictates that if the original searches are proven to violate Ulbricht's rights, then all evidence collected thereafter cannot be used.
