Using bots to test millions of username/password combinations leaked from previous data breaches on different platforms.

Attackers feed these lists into automated software that systematically tests thousands of login pairs against different websites until a match is found. NordStellar Security Risks and Recommendations

: "High Quality" valid credentials, often marketed as "fresh" or currently active to attract buyers. : A text file (usually formatted as email:password

This refers to the compression format or the delivery method of the data package. How Combolists are Generated