The data is rarely from a single new breach. Instead, it is a compilation of information from older leaks, "stealer logs" (data harvested by infostealer malware), and phishing campaigns.

If your email and a password you use appear in this file, attackers can take over your social media, banking, or corporate accounts.

These "MIX" text files are primarily used by attackers for credential stuffing , where automated scripts try combinations across various websites to gain unauthorized access to accounts.

This provides a critical second layer of security even if an attacker has your password.