Channel 4 News exposes the "hidden web", a shady network of websites trading in illegal goods, including drugs and paedophile material, apparently beyond the grasp of the authorities.

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There's the internet most of us know and use; websites with friendly names which operate publicly, trade legitimately and are easily found using search engines.

But beyond this there is another internet.

The websites have deliberately obscure addresses and cannot be found by accident, and they are not indexed by any search engines. In order to access them a user must download special software - and when they access the sites, the technology means that they do so anonymously.

Some of the sites are nothing more than a hidden club for geeks. But when Channel 4 News accessed the "dark web", sometimes known as the "hidden web", we found a marketplace flooded with illegal goods and services.

Firearms, drug making paraphernalia, any illegal commodity...They'll bury it in one of these underground cyber supermarkets. Detective Superintendent Charlie McMurdie

Forged passports, stolen credit card details, and hardcore drugs are all openly offered for sale and - most worryingly - there are scores of sites offering images of child sexual abuse.

Dark web: the internet behind our own and the money which fuels it (Getty)

The head of the Metropolitan Police e-crime unit, Detective Superintendent Charlie McMurdie, told Channel 4 News the dark web was a major "enabler" of crime.

"These sites are the main place where cyber criminals trade data, trade hacking kits, tools, techniques. So it's a real enabler that facilitates loads of other types of criminality."

She said that many kinds of illegal goods are available.

"Firearms, drug-making paraphernalia, hacking kits, compromised data, any illegal commodity, that's where they are going to trade," she said.

"They'll bury it in one of these underground cyber supermarkets."

Sites in the dark web sell different kinds of illegal goods (screen grab)

The underground sites are also a magnet for paedophiles operating online, with scores of sites offering images of child sexual abuse. One child protection expert told Channel 4 News he believes it is attracting the hard-core of paedophiles - including so-called "contact offenders", who have access to children and are using that access to create material for distribution to others.

Expert Mark Williams-Thomas said: "The material they are producing or sharing or discussing is absolutely horrific, so what we need to do is change the way we police.

"For a long time now we have policed the internet in a reactive way, which is how we police generally - in other words we wait for a phone call then we respond to it. What we need to do is become proactive, we need to start hitting the underworld, the sites that exist under the surface.

We need to become proactive, we need to start hitting the underworld. Mark Williams-Thomas

"And until we start doing that and changing the way we police we're not going to make a significant difference."

Anonymous

The software which is used to gain access to the sites disguises the computer's IP address, meaning that police cannot track offenders. Police have previously relied on tracing payments, but now more and more the criminals have been using a global system of online credits called Bitcoins - which have the advantage of being anonymous.

Professor Peter Sommer, a cyber expert at the London School of Economics, told Channel 4 News: "These schemes are devised by geeks who are interested in the problem of anonymity, how you can pass on information or do deals anonymously, but they obviously get mostly used by criminals. So they are deliberately hidden."

Bitcoins pass between computers rather than individuals. They are bought using "real world money" and can then be spent online. Bitcoins can also be exchanged back into real money.

According to their Twitter feed, the hacking group LulzSec accumulated a Bitcoin account worth several thousand US dollars.

The fact that Bitcoins are untraceable means the police can't just follow the money. So cracking down on this version 2.0 of the black market could prove to be a headache.

But police are adamant that they have the situation under control.

Ms McMurdie told Channel 4 News: "We have proven a number of times in the past that they will be arrested, we will identify who they are, we have conducted prosecutions and brought these people to court.

"The technology which is often used by cyber criminals - that's something that law enforcement have to exploit as well."

Watch the video below to find out more about how the Met is tackling the dark web.

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