The UK government has launched a dedicated cybercrime unit to tackle the Dark Web. But what is that? We explain what is the Dark Web, how it differs from the Deep Web, and how to access the Dark Web. Plus: the Deep Web, the Deepnet, the Invisible Web, the Hidden Web and the Dark Internet. Everything you need to know about the hidden internet. (Image by TheAutomotovatedCyclist.)

Update 28 April 2016: The latest site to fall victim to hackers is BeautifulPeople.com, and around 1.1 million members' personal details, including their names, addresses, sexual preference, relationship status, phone numbers, email addresses and even private messages have been leaked on to the Dark Web following a hack in December 2015.

Update 3 March 2016: The Dark Web hit the headlines in August 2015 after it was been reported that 10GB of data stolen from Ashley Madison, a site designed to enable bored spouses to cheat on their partners, was dumped on to the Dark Web. Hackers stole the data and threatened to upload it to the web if the site did not close down, and it has now acted on that threat. Now the spouses of Ashley Madison users have begun to receive blackmail letters demanding they pay $2500 in Bitcoin or have the infidelity exposed.

Update 9 November 2015: The UK government has launched a dedicated cybercrime unit to tackle the Dark Web, with a particular focus on cracking down on serious crime rings and child pornography. The National Crime Agency (NCA) and UK intelligence outfit GCHQ are together creating the Joint Operations Cell (JOC).

What is the Dark Web?

The Dark Web is a term that refers specifically to a collection of websites that are publicly visible, but hide the IP addresses of the servers that run them. Thus they can be visited by any web user, but it is very difficult to work out who is behind the sites. And you cannot find these sites using search engines.

Almost all sites on the so-called Dark Web hide their identity using the Tor encryption tool. You may know Tor for its end-user-hiding properties. You can use Tor to hide your identity, and spoof your location. When a website is run through Tor it has much the same effect.

Indeed, it multiplies the effect. To visit a site on the Dark Web that is using Tor encryption, the web user needs to be using Tor. Just as the end user's IP is bounced through several layers of encryption to appear to be at another IP address on the Tor network, so is that of the website. So there are several layers of magnitude more secrecy than the already secret act of using Tor to visit a website on the open internet - for both parties (See also: How to delete your Google location history).

Not all Dark Web sites use Tor. Some use similar services such as I2P - indeed the all new Silk Road Reloaded uses this service. But the principle remains the same. The visitor has to use the same encryption tool as the site and - crucially - know where to find the site, in order to type in the URL and visit.

Infamous examples of Dark Web sites include the Silk Road and its offspring. The Silk Road was (and maybe still is) a website for the buying and selling of recreational drugs. But there are legitimate uses for the Dark Web. People operating within closed, totalitarian societies can use the Dark Web to communicate with the outside world. And given recent revelations about US- and UK government snooping on web use, you may feel it is sensible to take your communication on to the Dark Web. (I'll stick to Facebook, but I like the attention.) See also: What does Google know about me?

Dark Web or Deep Web? (Or Deepnet, Invisible Web, or Hidden Web?)

Although all of these terms tend to be used interchangeably, they don't refer to exactly the same thing. An element of nuance is required. The 'Deep Web' refers to all web pages that search engines cannot find. Thus the 'Deep Web' includes the 'Dark Web', but also includes all user databases, webmail pages, registration-required web forums, and pages behind paywalls. There are huge numbers of such pages, and most exist for mundane reasons.

We have a staging version of all of our websites that is blocked from being indexed by search engines, so we can check stories before we set them live. Thus for every page publicly available on this website (and there are literally millions), there is another on the Deep Web. The content management system into which I am typing this article is on the Deep Web. So that is another page for every page that is on the live site. Meanwhile our work intranet is hidden from search engines, and requires a password. It has been live for nearly 20 years, so there are plenty of pages there.

Use an online bank account? The password-protected bits are on the Deep Web. And when you consider how many pages just one Gmail account will create, you understand the sheer size of the Deep Web.

This scale is why newspapers and mainstream news outlets regularly trott out scare stories about '90 percent of the internet' consisting of the Dark Web. They are confusing the generally dodgy Dark Web with the much bigger and generally more benign Deep Web. Mixung up the act of delibarately hiding things, with that of necessarily keeping pages away from search engines for  reasons of security or user experience. (See also:How to use torrent sites in UK: how to access The Pirate Bay, blocked torrents.)

Wait, what about the 'Dark Internet'?

Confusingly, 'Dark Internet' is also a term sometimes used to describe further examples of networks, databases or even websites that cannot be reached over the internet. In this case either for technical reasons, or because the properties contain niche information that few people will want, or in some cases because the data is private.

A basic rule of thumb is that the phrases 'Dark Web' or 'Deep Web' are typically used by tabloid newspapers to refer to dangerous secret online worlds, the 'Dark Internet' is a boring place where scientists store raw data for research. The Deep Web is a catch-all term for all web pages that are not indexed for search, the others refer to specific things. (See also: Take precautions when using public Wi-Fi networks.)

How to access the Dark Web

Technically, this is not a difficult process. You simply need to install and use Tor. Go to www.torproject.org and download the Tor Browser Bundle, which contains all the required tools. Run the downloaded file, choose an extraction location, then open the folder and click Start Tor Browser. That's it. The Vidalia Control Panel will automatically handle the randomised network setup and, when Tor is ready, the browser will open; just close it again to disconnect from the network.

Depending on what you intend to do on the Dark Web, some users recommend placing tape over your laptop's webcam to prevent prying eyes watching you. A tinfoil hat is also an option.

The difficult thing is knowing where to look. There, reader, we leave you to your own devices and wish you good luck and safe surfing. And a warning before you go any further. Once you get into the Dark Web, you *will* be able to access those sites to which the tabloids refer. This means that you could be a click away from sites selling drugs and guns, and - frankly - even worse things.

Aggregation sites such as Reddit offer lists of links, as do several Wikis, including http://thehiddenwiki.org/  - a list that offers access to some very bad places. Have a quick look by all means, but please don't take our linking to it as an endorsement.

Also, Dark Web sites do go down from time to time, due to their dark nature. But if you want good customer service, stay out of the dark!

And do heed our warning: this article is intended as a guide to what is the Dark Web - not an endorsement or encouragement for you to start behaving in illegal or immoral behaviour.

You can find an in-depth guide to using Tor here.