United States and European authorities have arrested 16 suspected members of underground drugs and weapons cybermarkets this week, including the alleged operator of the website known as Silk Road 2.0.

The Federal Bureau of Investigation (FBI) has been investigating Silk Road 2, the successor website to Silk Road, since it popped up in October 2013.

US authorities said they had shut down the underground online drugs marketplace and charged its alleged operator, Blake Benthall, with conspiracy to commit drug trafficking, computer hacking, money laundering and other crimes.

According to police, Benthall used his own personal email address to register for the servers used to run the illegal drug market, blake@benthall.net.

It also revealed that a US Government agent had been a central organising figure on the site since its early days.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 5 minutes 1 second 5 m Listen to Will Ockenden's report Download 9.2 MB

The FBI said the Silk Road 2.0 site had allowed 100,000 people to buy or sell drugs over the internet.

The US Government said the site had been processing sales of about $8 million per month.

In a sweep across 18 countries, FBI and Europol netted $1 million worth of digital currency Bitcoin and about $260,000 in cash, silver, gold and narcotics.

About 400 internet sites and domains, which had been used to sell child pornography, guns and murder-for-hire, were taken down on Thursday.

Users are reporting several other dark web sites have also been taken down, including Hydra, Pandora, Onion Shop, Cloud 9 and Alpaca.

The original Silk Road website was raided and taken offline in October 2013. Silk Road 2.0 emerged just five weeks later

Darknet 'neither invisible nor untouchable'

The illegal organisations used the Tor computer network which allows users to communicate anonymously by masking their IP address, to run so-called "dark" markets.

Troels Oerting, the head of Europol's cybercrime centre, said the operation had knocked out a significant part of the infrastructure for illegal online drugs and weapons trade in the countries involved but black market websites had mushroomed and were created easily.

"We have also hit services on the Darknet using Tor where, for a long time, criminals have considered themselves beyond reach," Mr Oerting said.

"We can now show that they are neither invisible nor untouchable."

The internet's black market Drug dealers shed light on the growing online black market which is helping more and more Australians buy weapons and drugs. Read the full report by the ABC's Conor Duffy.

Patrick Gray, IT security journalist and presenter of the Risky Business podcast said the dark web had initially attracted criminals as a safer business alternative.

"These online market places are used to sell pretty much anything illicit, that's really what they're there for," Mr Gray said.

"There's a perception among criminals that it's a safer way to do business."

Mr Gray said it would not have been a difficult investigation for the police, as the alleged operator made fundamental errors in securing the website.

"In this case it didn't help the operator of Silk Road 2 that they made some pretty fundamental, operational security mistakes and also one of the moderators of the website from pretty early on turned out to work for the US Federal Government as an investigator," Mr Gray said.

"This Federal agent had developed a persona already in the underground sort of dark net scene and they were actually invited into a discussion around Silk Road 2 and eventually were more or less offered a job as a moderator.

"There's that famous old New Yorker cartoon which says you know 'on the internet no-one knows you're a dog'. Well on the internet no-one knows if you're a Fed either and that seems to be what stung these operators."

The website's failure to secure itself has also left open the likely possibility that the details of all the users are also in the hands of police.

"The US government first became aware of the physical location of the Silk Road 2, the computers that run the Silk Road 2 - I think in May 2014," Mr Gray said.

"You can safely assume that anything that happened after May 2014, it's highly within the realm of possibility that everything after that point was monitored by the US Government."

ABC/Reuters