Reused credentials, new targets
Credential stuffing involves trying username and password pairs exposed elsewhere against another service. It differs from guessing arbitrary passwords.
Why individual failures aren’t enough
A failed login may be an ordinary mistake. A pattern across accounts and attempts deserves a closer look, but does not establish malicious intent by itself.
Use multiple defenses
Multi-factor authentication can reduce the risk from stolen passwords. Combine it with appropriate login protections and an investigation process. No single signal should be treated as a complete answer.
Further reading
This is an introductory overview, not a comprehensive security assessment. For deeper implementation guidance, see OWASP: Credential Stuffing Prevention.