The criminals behind most data breach events are after money. Once they are able to obtain a large volume of personal information, they usually put it up for sale on various online forums, typically on the dark web.
The dark web is a hidden layer of the internet, inaccessible on normal search engines–specific software is required to access it. The dark web is popular with cybercriminals as it offers anonymity and is mostly untraceable.
Once data is obtained, criminals can use it to file fraudulent tax returns, pay for medical costs, file for unemployment, open credit card accounts, and apply for various loans.