File picture: Elise Amendola

London - The internet is like an iceberg. The web as we know it – every Google result, all the billions of sites we visit – is just a tiny fraction jutting above the waves. The vast majority of it is invisible to web browsers and the general public. This is known as the “dark web”.

Most of this unseen mass of activity is perfectly innocent – paid-for content, sites that require log-ins, academic data, and so on. No one knows exactly how big the “dark” part is, but it’s estimated to be at least 15 times larger than the web we know, with more than 900 billion pages.

The dark web is a haven for criminal gangs around the world, to whom it offers a secret shop window where everything from child pornography to hard drugs to stolen credit-card details can be bought and sold.

The “anonymous” web browser Tor is used by about 600 000 people a day – and is totally untraceable. Tor “bounces” data between dozens of computers on its way to and from the web, making users effectively invisible.

Financed by the US government, the controversial browser is used by the FBI and championed by advocates of internet freedom. Tor offered a “safe” channel to Egyptian dissidents during the Arab Spring and is used by bloggers in Syria. But it also grants access to a world where the illegal is openly traded.

Using Tor, you can visit special “.onion” sites – a dark domain that is used to host highly illegal marketplaces. The notorious Silk Road site is an open drug market, where you browse and use a “checkout basket”, much as you would on Amazon. This week, offers include “250 pills of speed”, grams of Afghan heroin and new synthetic drugs.

Users report that contract killers can be hired via other Tor sites – and that fights to the death are a spectator sport. Many transactions are paid for in “bitcoins”, an online currency that allows money to be transferred without using banks.

Tor users in the UK openly offer weapons, high-grade cocaine and brides for sham marriages. Cyber criminals also advertise their wares.

One hacker’s .onion site proclaims: “I’ll do anything for money. If you want me to destroy some bussiness or a persons life [sic], I’ll do it! I can ruin them financially … If you want someone to get known as a child porn user, no problem.”

David Emms, senior researcher at internet security company Kaspersky Lab, said: “The dark market is the underbelly of the legitimate economy, but it operates in a similar way.

“If criminals want to trade, they have to have a point of presence. Once you’ve found them, they’ll do business via sites on the hidden web or fake email accounts. The key is they’re quite prepared to move. When the corrupt internet service provider Russian Business Network was shut down, a lot of people predicted that was the end of the dark market, but they just reappeared elsewhere.” – Mail On Sunday