A data leak is the unauthorized release or loss of sensitive information. This includes usernames, passwords, credit card numbers, or other information essential for privacy protection. These data leaks affect companies, organizations, and individuals.  As a result, large amounts of data are stored in so-called leak databases — a type of online database containing billions of records. The data can come from various sources, such as leaks, hacker attacks, public databases, and illegal social engineering attacks. The databases are often hidden behind a paywall and used for other purposes besides investigations.  However, these databases differ from helpful offers such as the Pwned database, Leak Checker, and Identity Leak Checker, which also establish relationships between passwords and users. These collections now contain more than 40 billion data records.