They are aggregated from thousands of different data breaches, phishing campaigns, and infostealer malware logs .

A is essentially a massive text file containing pairs of usernames (or emails) and passwords. Unlike a raw database dump from a single website, these lists are often curated and cleaned to be used in automated "credential stuffing" attacks.

Despite being labeled "fresh," many lists are "recycled" or "stale," containing data from breaches that occurred years ago. Researchers found that much of the data in these public dumps is already known or invalid. Why This Matters to You