Credential Stuffing

Credential stuffing takes username and password pairs leaked from one breach and replays them against login forms on unrelated services. It works because people reuse passwords. When a billing site leaks a corpus of credentials, an attacker knows a meaningful fraction of those same pairs will unlock accounts on email providers, retailers, and corporate portals.

The attack is high-volume and automated. Tools drive millions of login attempts through proxy pools and headless browsers, rotating IPs to dodge rate limits and solving or bypassing weak bot defenses. A low success rate still yields many valid accounts when the input list runs into the millions. Unlike password guessing, the attacker is not brute-forcing a single account; they are testing known-good pairs broadly.

Defenders counter with multi-factor authentication, which breaks the attack even when the password is correct, plus rate limiting, breached-password checks, and anomaly detection. A spike of failed logins from scattered IPs is a signal that good intrusion detection catches, and a confirmed account takeover kicks off incident response.

In a Trickest workflow, you fold threat intelligence on newly leaked credential dumps into a pipeline that cross-checks your own user base, flags reused passwords, and forces resets before an attacker replays them.