2014 saw the continued growth of the dark web, a collection of underground websites that allow people to engage in often-illegal activities beyond the reach of law enforcement. Here's what the dark web is, how it works, and why it's not going away any time soon.

What is the dark web?

The dark web is a general term for the seedier corners of the web, where people can interact online without worrying about the watchful eye of the authorities. Usually, these sites are guarded by encryption mechanisms such as Tor that allow users to visit them anonymously. But there are also sites that don't rely on Tor, such as password-protected forums where hackers trade secrets and stolen credit card numbers, that can also be considered part of the dark web.

People use the dark web for a variety of purposes: buying and selling drugs, discussing hacking techniques and selling hacking services, trading child pornography, and so forth.

It's important to remember that the technologies used to facilitate "dark web" activities aren't inherently good or bad. The same technologies used by drug dealers and child pornographers to hide their identity can also be used by whistleblowers and dissidents in repressive regimes.

What's Tor? Why is it important for the dark web?

Tor, which stands for "the onion router," is a technology that allows people to browse the web and access online services without revealing their identities. The Tor network consists of thousands of servers located all over the world. They're run by volunteers seeking to bolster privacy rights.

When you browse the web using a Tor-based browser, your communications are automatically bounced off of several Tor servers before they reach their destination. The process makes it almost impossible for anyone to trace the traffic back to you. According to documents released by Ed Snowden, even the NSA has struggled to unmask Tor users.

Tor allows the creation of hidden services, websites that use the Tor network to hide their physical location. This technology has allowed the creation of websites devoted to illegal activities that are difficult for the authorities to trace and shut down.

Surprisingly, Tor was created with financial support from the US government, which wanted to promote the free flow of information. Government support for Tor has continued in recent years as part of the State Department's internet freedom agenda, which seeks to help people in repressive regimes gain access to information censored by their governments.

While Tor has many illicit uses, it also has a lot of legitimate ones. For example, Facebook recently announced a version of its website that can be accessed over the Tor network, which will make it easier to access the site from countries that restrict the service, such as China and Iran.

What kind of information can you find on the dark web?

Almost any type of illegal and legally questionable products and services can be found somewhere in the internet's underground.

One of the best examples is the Silk Road, a now-defunct website that, for more than two years, operated as a kind of illicit eBay. The Silk Road was most famous for offering a wide variety of illegal drugs, but it offered other illicit products as well. You could buy fake IDs, pirated DVDs, fireworks, and stolen credit-card numbers.

The Silk Road website was a Tor hidden service, which made it difficult for the authorities to shut the site down. All transactions were conducted using Bitcoin, meaning they couldn't be traced the way credit-card transactions can be. But eventually, law enforcement was able to identify the site's alleged operator, who was arrested in 2013.

Almost immediately, copycat sites sprang up. A successor site called Silk Road 2 was founded in 2013, but it was infiltrated by law enforcement and shut down in 2014. Currently, one of the largest Silk Road successors is a site called Evolution. Ars Technica recently reported that it had 26,000 product listings.

Even these sites had some lines they weren't willing to cross. For example, all three sites barred child pornography listings. But other dark web sites exist to help users find and distribute this kind of material. A recent study by computer scientist Gareth Owen suggested that sites related to child abuse and child pornography could account for as much as 80 percent of traffic to Tor hidden services (though hidden services account for a small fraction of Tor traffic overall).

Why has Bitcoin become popular on dark web sites?

If you tried to set up an illicit drug marketplace that used conventional credit cards, it wouldn't last very long. For one thing, Visa and Mastercard rules would likely bar you from getting a merchant account. And customers would be wary of using a credit card linked to their real identity to make illicit purchases. You'd also have to worry about customers reversing charges after the goods had been delivered, since you can't exactly go to the authorities if your customers rip you off.

In short, a digital black market needs the digital equivalent of cash. And that's exactly what Bitcoin is. Bitcoin, like cash, allows transactions to be made anonymously. And with no one in charge of the Bitcoin network, there's no one with the authority to block illicit transactions.

But we shouldn't overstate Bitcoin's anonymity. You don't need to prove your identity before using the Bitcoin network the way you do with credit cards. But that doesn't necessarily mean the authorities won't be able to trace buyers and sellers. Indeed, information about every Bitcoin transaction is publicly available; by examining the pattern of transactions, the authorities may be able to tie a Bitcoin transaction to a real-world identity.

For example, the authorities were allegedly able to prove that the founder of Silk Road 2 cashed out $273,626.60 worth of bitcoins, then used some of the cash to buy a brand new Tesla Model S. We don't know exactly how the authorities made this connection, but they may have subpoenaed the exchange that converted the bitcoins into dollars. Disguising bitcoin earnings is a complex and difficult task; one slip-up can reveal your real identity.

As with Tor, it's important to note that not all, or even most, uses of the Bitcoin network are for illicit purposes. There are tens of thousands of legitimate businesses that accept Bitcoin. But criminals have been attracted to Bitcoin for the same reasons they've been attracted to conventional cash.

Is the dark web the same thing as the deep web?

No, the deep web is a broader concept. It refers to all online content that's not accessible to search engines. That includes the internet's underground economy, but it also includes mainstream websites that simply aren't set up for Google's and Bing's web crawlers. For example, most of Facebook is part of the deep web: most Facebook content is only available to the poster's friends, not the general public. Similarly, many searchable databases won't come up in Google results even though anyone can access them.

Can the authorities ever stamp out the dark web?

The government is unlikely to ever fully suppress the dark web for the same reason that law enforcement has never been able to eliminate conventional black markets: there's a lot of demand for the information and products offered on these sites, and there's always going to be someone willing to take the risks involved in meeting that demand.

And these sites can earn a lot of money. Silk Road 2, for example, reportedly earned $8 million in a single month before it was shut down. That kind of money will always attract copycats who believe they can succeed where their predecessors had failed.

Moreover, the government probably can't — and shouldn't — shut down the underlying technologies that make the dark web possible. Tor provides crucial protection to dissidents and whistleblowers around the world. Bitcoin has the potential to produce significant innovations in the payments business. And shutting down these technologies won't stop people from using the internet for illicit purposes. Most likely, these activities will simply shift overseas, where they will be even harder for American authorities to police.