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The so-called dark web, a portion of the hidden internet, is usually associated with a host of illegal activities including the buying and selling of drugs, firearms, stolen financial data and other types of valuable information. The selling point? Total anonymity. That may sound nefarious, but some experts argue that the dark web is also useful in circumventing internet censorship. While most people spend their time online on what is known as the surface web — the portion of the World Wide Web that can be accessed with standard browsers and search engines — it has become relatively easy for anyone to access the dark web.

The dark web is a small subset of the deep web, which is part of the internet that is not found using search engines. That includes many websites that require users to log in with an username and password, and the deep web is estimated to be about 400 to 500 times larger than the common internet. The dark web is relatively smaller — it is made up of a series of encrypted networks that is able to hide users' identities and locations and can only be accessed with special software. The most popular of those networks is called TOR, or The Onion Router, which was developed initially for government use before it was made available to the general public. "When people typically refer to the dark web, a lot of the time they're referring to a portion of the internet that's accessible using an anonymous browsing network called TOR," Charles Carmakal, a vice president at cybersecurity firm FireEye, told CNBC's "Beyond the Valley" podcast. One of the primary functions of the TOR network is that it allows users to access ".onion" pages, which are specially encrypted for maximum privacy. Carmakal explained that TOR also lets users connect to normal websites anonymously so that their internet service providers cannot tell what they're browsing. Similarly, the websites will not be able to pinpoint the location of the users browsing their pages. On the TOR browser, the connection requests are re-routed several times before reaching their destination. For example, if a user in Singapore is trying to connect to a website in London, that request on a TOR browser could be routed from Singapore to New York to Sydney to Capetown to, finally, London.

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According to Carmakal, a service like TOR is a useful tool for many users to bypass state censorship and crackdowns on the internet. With it, he said, they can communicate with the free world without any repercussions. The service is also used by journalists and law enforcement, he said. Still, the term dark web today is commonly associated with illegal activities. In recent years, a number of high-profile marketplaces on the dark web were taken down for selling drugs and other contraband, including Silk Road, AlphaBay and Hansa. Law enforcement agencies around the world have been working hard to take down communities on the dark web that criminals use, according to James Chappell, co-founder of a London-based threat intelligence company Digital Shadows.