The dark web is the World Wide Web content that exists on darknets: overlay networks that use the Internet but require specific software, configurations, or authorization to access.[1][2][3][4] Through the dark web, private computer networks can communicate and conduct business anonymously without divulging identifying information, such as a user’s location.[5][6] The dark web forms a small part of the deep web, the part of the Web not indexed by web search engines, although sometimes the term deep web is mistakenly used to refer specifically to the dark web.[7][2][8]

The darknets which constitute the dark web include small, friend-to-friend peer-to-peer networks, as well as large, popular networks such as Tor, Freenet, I2P, and Riffle operated by public organizations and individuals.[6] Users of the dark web refer to the regular web as Clearnet due to its unencrypted nature.[9] The Tor dark web or onionland[10] uses the traffic anonymization technique of onion routing under the network’s top-level domain suffix .onion.

Web-based onion services in January 2015[19]
Category Percentage
Gambling
0.4
Guns
1.4
Chat
2.2
New
(not yet indexed)
2.2
Abuse
2.2
Books
2.5
Directory
2.5
Blog
2.75
Porn
2.75
Hosting
3.5
Hacking
4.25
Search
4.25
Anonymity
4.5
Forum
4.75
Counterfeit
5.2
Whistleblower
5.2
Wiki
5.2
Mail
5.7
Bitcoin
6.2
Fraud
9
Market
9
Drugs
15.4
Web-based onion services in February 2016[20][21]
Category % of total % of active
Violence
0.3
0.6
Arms
0.8
1.5
Illicit Social
1.2
2.4
Hacking
1.8
3.5
Illicit links
2.3
4.3
Illicit pornography
2.3
4.5
Extremism
2.7
5.1
Illicit Other
3.8
7.3
Illicit Finance
6.3
12
Illicit Drugs
8.1
15.5
Non-illicit+Unknown
22.6
43.2
Illicit total
29.7
56.8
Inactive
47.7
Active
52.3
A December 2014 study by Gareth Owen from the University of Portsmouth found that the most commonly hosted type of content on Tor was child pornography, followed by black markets, while the individual sites with the highest traffic were dedicated to botnet operations (see attached metric).[22] Many whistleblowing sites maintain a presence[23] as well as political discussion forums.[24] Sites associated with Bitcoin, fraud-related services, and mail order services are some of the most prolific.[22]

As of December 2020, the number of active Tor sites in .onion was estimated at 76,300 (containing a lot of copies). Of these, 18 000 would have original content.[25]

In July 2017, Roger Dingledine, one of the three founders of the Tor Project, said that Facebook is the biggest hidden service. The dark web comprises only 3% of the traffic in the Tor network.[26]

A February 2016 study from researchers at King’s College London gives the following breakdown of content by an alternative category set, highlighting the illicit use of .onion services.[17][27]

There have been arguments that the dark web promotes civil liberties, like “free speech, privacy, anonymity”.[5] Some prosecutors and government agencies are concerned that it is a haven for criminal activity.[80] The deep and dark web are applications of integral internet features to provide privacy and anonymity. Policing involves targeting specific activities of the private web deemed illegal or subject to internet censorship.

When investigating online suspects, police typically use the IP (Internet Protocol) address of the individual; however, due to Tor browsers creating anonymity, this becomes an impossible tactic.[81] As a result, law enforcement has employed many other tactics in order to identify and arrest those engaging in illegal activity on the dark web.[82] OSINT, or Open Source Intelligence, are data collection tools that legally collect information from public sources.[81] OSINT tools can be dark web specific to help officers find bits of information that would lead them to gaining more knowledge about interactions going on in the dark web.[81]

In 2015 it was announced that Interpol now offers a dedicated dark web training program featuring technical information on Tor, cybersecurity and simulated darknet market takedowns.[83] In October 2013 the UK’s National Crime Agency and GCHQ announced the formation of a “Joint Operations Cell” to focus on cybercrime. In November 2015 this team would be tasked with tackling child exploitation on the dark web as well as other cybercrime.[84] In March 2017 the Congressional Research Service released an extensive report on the dark web, noting the changing dynamic of how information is accessed and presented on it; characterized by the unknown, it is of increasing interest to researchers, law enforcement, and policymakers.[85] In August 2017, according to reportage, cybersecurity firms which specialize in monitoring and researching the dark web on behalf of banks and retailers routinely share their findings with the FBI and with other law enforcement agencies “when possible and necessary” regarding illegal content. The Russian-speaking underground offering a crime-as-a-service model is regarded as being particularly