These lists are aggregated from multiple historical data breaches or harvested recently via infostealer malware (e.g., RedLine, Lumma) that scrapes login data directly from infected devices.
Files hosted on suspicious sites for download are often bundled with malware designed to infect the downloader's own computer.
They are often formatted as email:password to be easily read by automated cracking tools like OpenBullet or SilverBullet .