US federal officials and European law enforcement groups in over a dozen countries said Friday that they shut down more than 400 illegal websites -- uncovering the tracks of website operators even as those operators used specialized anonymity software.
Authorities said they made the arrests by figuring out the identities of Tor users. Tor is free software meant to encrypt, or hide, actions on the Internet. While the law enforcement officials said they identified website operators who were using the software, Internet security experts told The Wall Street Journal that it's unlikely they actually cracked through Tor's complicated encryptions.
The websites, or so-called "dark markets," were selling illicit goods including illegal narcotics, firearms, stolen credit card data and counterfeit currency, the FBI said. Authorities also arrested 17 people, seized computer hardware, cryptocurrency bitcoins worth $1 million and more than $200,000 in cash, drugs, gold and silver.
The announcements from the FBI and European authorities came a day after US federal officials said they had arrested Blake Benthall, a 26-year-old identified in connection with the operation and ownership of Silk Road 2.0. The illegal marketplace was similar to the original Silk Road site, which was shut down more than a year ago.
Tor -- originally TOR, or "The Onion Router" -- was first developed by the US Naval Research Laboratory and is currently funded in part by the US State Department and Department of Defense. By unveiling the identities of the website operators, authorities signaled they may have gotten more than a fleeting grasp on one of the hidden corners of the Internet.
The software facilitates anonymous Web surfing, forum posting, instant messaging, and other Internet communication by wrapping signals in layers of encryption and then sending them on an unpredictable path through a network of routers. Each router peels off one "skin" of encryption to send the signal along, but no one router has access to all the details -- thus the signal can't be traced back to its sender.
"It is a plain fact that criminals use advanced technology to commit their crimes and conceal evidence," Assistant Attorney General Leslie R. Caldwell of the Justice Department's Criminal Division said in a statement. "But the global law enforcement community has innovated and collaborated to disrupt these 'dark market' websites, no matter how sophisticated or far-flung they have become."
CNET's Seth Rosenblatt contributed to this report.