Credential stuffing explained simply
Credential stuffing doesn't use magic, but mass: leaked credentials are automatically tried out on many other services.
What credential stuffing actually means
Credential stuffing describes automated login attempts with already known username and password combinations. So the attack is based on reuse, not guessing a new password.
That's why even a medium-sized leak is dangerous if users have used their passwords multiple times.
Why the attack is so successful
- Many users recycle credentials across multiple services.
- Automated tools can quickly test large volumes of logins.
- A successful hit often opens chain access via recovery and connected accounts.
How to protect yourself against it
The strongest defense is surprisingly simple: a unique password per account. Then a leaked access immediately loses its added value for other services.
Additionally, MFA, rate limits and leak warnings help to further reduce the attack surface.
Quick checklist
The most important actions from this guide in compact form.
- Consistently eliminate reuse.
- Turn on MFA for main accounts.
- After leaks, immediately replace all affected passwords.
Common questions
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Brute Force vs. Password Spraying: What's the Difference?
If you want to keep going, this is the next guide to read.
Brute force and password spraying are both login attacks, but they differ in whether they test many passwords against one account or a few passwords against many accounts.