The darknet has a reputation for being a criminal haven, chock full of illegal goods, stolen credentials, illicit message boards, and so on. While this is not untrue, and the darknet does contain an overwhelming amount of stolen data and illegal activity, there are many uses for the darknet that are completely legitimate.
Lawful uses of the darknet
While most of what you've likely heard or read about the darknet and dark web sites involves illegal or nefarious activity, there are many legal uses for the darknet. Many people care about their privacy and would like to keep their legal, online activity private from surveillance and monitoring by third parties, including internet service providers, businesses, and governments. Here are some non-criminal ways the darknet is used:
People living or working in countries being led by oppressive regimes will often take to the darknet for a myriad of reasons, including to obtain access to the internet in areas where the internet is restricted, political activism or revolutionary action and the spread of information and secure communication for non-governmental organizations (NGO) or private sector employees in unstable nations.
Security researchers utilize the darknet as a source of information on computer software and hardware, exploits, tools, etc.
The FBI and other law enforcement groups use the darknet for sting operations or to keep governmental IP addresses out of web logs.
Members of the military intelligence community use the darknet as a source of OSINT, open-source intelligence information - information that is publicly available.
Many journalists leverage the darknet for encrypted communications to protect both themselves and their source(s). Journalists also use the darknet to avoid censorship.
Home automation platforms, which are used to access manage, and control the internet of things (IoT), are turning to the darknet's hidden services to leverage its secure communication connection against malicious threat actors.
Social media. For example, there's even a Facebook .onion site (link is to the about page, not the darknet site).
While of course there are valid uses for the anonymity offered by the darknet, there are indeed a vast number of criminals who take advantage of these hidden services as the lure of anonymity tends to attract those attempting to evade law enforcement and other authorities. The largest volume of darknet sites involve drugs, darknet markets (darknet sites for the buying and selling of goods and services), and fraud.
Criminal uses of the darknet
Credit card numbers and other personally identifiable information (PII) can be purchased on the darknet for theft and fraud activities.
Counterfeiters offer document forging and currency imitation services.
A variety of darknet markets (black markets) allow for the anonymous, illegal buying and selling of drugs and other illegal or controlled substances, such as pharmaceuticals, and weapons.
Blackhat hackers brag about their exploits, communicate and collaborate with other hackers and share security exploits (vulnerabilities they can leverage to gain access to software, hardware, data, etc.).
Gamblers take to the darknet to skirt local gambling laws and engage in illegal gambling activity.
Terrorists use the darknet for internet access, recruiting, sharing of information, and organizing.