Troy Hunt, the founder of the resource, talked about this. As it turns out, this information is scattered throughout the Telegram channels of various hacker groups.
Information in such channels and groups is often presented in the form of username and password combinations; Hackers obtain this data through credential automated filling or extraction from leaked databases. Researchers reported that they found login information and passwords from e-mail addresses captured on Telegram and created a database weighing 122 GB.
Source: Ferra

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