ISIS uses it. The Ashley Madison hackers used it. But chances are, you're not so familiar with the so-called "dark web," a hidden network of websites that requires special tools to access.
The appeal of such a network is obvious: Users can remain anonymous if they play their cards right, which means they can exchange sensitive information and make illicit business deals without fear of retaliation from law enforcement.
To put it in the most basic terms, the Internet exists in a few different layers. The one you're most accustomed to navigating is the "surface web," which is made up of content that search engines like Google are able to crawl, index and deliver to you. In other words, the surface web is any portion of the Internet that you could find from a basic Google Search -- probably most of the websites that the vast majority of us use in our day-to-day lives. The Huffington Post exists on the surface web, for example.
Then, there's the "deep web" -- not to be confused with the dark web, which is a shadowy pocket of the deep web. (We'll get there!) As intelligence firm BrightPlanet explains, sites that exist on the deep web are simply not accessible via search engines. You probably work on the deep web all the time: An online document you share with coworkers is one example, as are database entries that you have to search for within a website. So, there's nothing inherently illicit about the deep web, even if the term is often conflated with "dark web" and the criminal activities that can occur there.
Now for the exciting stuff.
Sites within the dark web use anonymity software, Wired notes, to ensure that visitors are basically untraceable. Tor is the most well-known example of that software.
Under normal circumstances, you could imagine a line between your computer (or phone) and whatever site it's connecting to. If you Google the phrase "IP address," you'll see the number that corresponds to your specific device and its real-world location. But if you were to use software like Tor, your computer would take a "random path" to its destination, bouncing around a variety of encrypted connections that ultimately mask your location and identity.
That's a simple way of thinking about it, but you can see why hackers, cyber criminals and whistleblowers would be attracted to communities on the dark web. Such communities allow them to share information and make business deals without fear of reprisal.
So, when hackers decided to release the identities of people who used the extramarital dating site Ashley Madison, they did it somewhere on the dark web, theoretically making themselves much harder for law enforcement to find.
For the same reason, people who sympathize with the militant Islamic State group communicate and even seek funding via the dark web. And, of course, an infamous black market called Silk Road operated much the same way, allowing people to buy and sell guns, drugs and child porn online, until it was shut down. (It says a lot about the dark web that copycats including Silk Road Reloaded have successfully launched following the closure of the first Silk Road.)
Similarly, the dark web is where hackers deposited data from the 2014 Sony Pictures Entertainment hack, unleashing droves of information that could have gone undetected for an untold number of days if the attackers hadn't publicized their work.
While law enforcement agencies have attempted crackdowns, recent research shows that illegal markets on the dark web still do millions upon millions of dollars in business every year. Silk Road met its untimely end in large part because its founder made sloppy mistakes off of the dark web.
All of this is to say: Much of it may seem unsavory, but the dark web is still a powerful tool harnessed regularly -- and one that certainly isn't going anywhere.
____
Damon Beres covers consumer technology, video games and the many ways humans interact with their devices. He is based in New York. You can contact him at damon.beres@huffingtonpost.com or on Twitter: @dlberes.
____