The Justice Department has shut down a major directory of dark web drug marketplaces and arrested the alleged owners in what federal prosecutors say is a first-of-its-kind operation.

"This is the single most significant law enforcement disruption of the darknet to date," U.S. Attorney Scott Brady said at a news conference Wednesday in Pittsburgh to announce the charges and the closing of the site DeepDotWeb.

The so-called darknet or dark web is a part of the internet that can be accessed only by specialized software or hardware and contains clandestine websites not found through normal search engines. DeepDotWeb was a regular searchable website that provided a directory with direct access to a host of darknet marketplaces selling illegal narcotics including fentanyl, cocaine, heroin and meth.

The website also provided access to marketplaces for firearms, including assault rifles, and for malicious software and hacking tools.

The alleged owners, Tal Prihar, 37, and Michael Phan, 34, both from Israel, were arrested Monday, Prihar in France and Phan in Israel, where they remain in custody. They each face a single count of money laundering conspiracy in the U.S. Phan also faces charges in Israel.

A marketplace Deep Dot Web led users to prior to its Department of Justice seizure. Department of Justice

Prihar and Phan allegedly received kickback payments through bitcoin when someone purchased an item on the darknet sites found through the directory, earning more than $15 million in fees since October 2013, according to prosecutors.

These "referral bonuses" allegedly came from darknet marketplaces including AlphaBay Market, Agora Market, Abraxas Market, Dream Market, Valhalla Market, Hansa Market, TradeRoute Market, Dr. D's, Wall Street Market and Tochka Market.

The closing of a directory like DeepDotWeb is significant, Brady said, because it should stifle hundreds of millions of dollars in illegal purchases.

The government has shut down major darknet drug marketplaces in the past, but they were quickly replaced by new ones. In July 2017, federal authorities in the U.S. shut down the AlphaBay and Hansa drug markets. But within days another darknet market had already picked up most of the listings, highlighting the challenge authorities face. Directories are the way many customers find darknet marketplaces, and the closure of a major directory was a first for the Justice Department.

"This prosecution is the first to attack the infrastructure supporting the darknet itself," Brady said.