https://www.cnet.com/news/old-hacks-strike-again-data-from-2b-accounts-lands-on-the-dark-web/

The compiled data doesn't come from any fresh breaches: Much of the information was accumulated in hacks like LinkedIn's 100 million breached accounts and Dropbox's 68 million stolen credentials, both of which happened in 2012. While this stolen data has been available for years, the massive collection conveniently puts it all in one download for people to use.

Researchers are referring to all that as Collection #2 through Collection #5, and it's one of the largest compilations of stolen credentials in history. It follows the 773 million email addresses released in Collection #1 earlier in January.