This is the best defense against credential stuffing, as a password alone will not grant access.

These lists are rarely from a single source. They are created by merging data from numerous security breaches, phishing scams, and infostealer logs.

Cybercriminals use these lists for "credential stuffing" or "brute-force" attacks, testing the pairs on various websites (banking, social media, e-commerce) to gain unauthorized access.