What is Credential Stuffing?

In credential stuffing, attackers test stolen or leaked credentials against other websites and services, usually through automated tools or a botnet. The attack exploits password reuse: one compromised account provides credentials that may still work elsewhere.

Why is Credential Stuffing dangerous?

Successful attacks can lead to fraudulent purchases, stolen customer data and takeover of business accounts. The method is widespread because it is easy to automate and large breach collections continuously provide new credentials, some of which remain valid.

What methods do attackers use in Credential Stuffing?

Credentials come from breach collections, criminal markets and infostealer logs. Attackers normalize this data and test it against payment services, shops, email providers and company portals. Traffic is distributed through changing proxies, making both attribution and simple IP blocking difficult.

When do Credential Stuffing attacks occur more frequently?

Globally organized credential stuffing attacks can be observed more frequently especially when, for example, a major service has been hacked and credentials are being sold on the darknet. APT groups are relatively quick here - especially when the APT's focus is financial gain.

How do I protect myself from Credential Stuffing?

A unique password for every service removes the attack's basic advantage, and a password manager makes this practical. Important services should also use 2FA or MFA, which can stop a login even when a third party has the correct password.

How do you prevent Credential Stuffing attacks on your own services?

Operators should limit login attempts by account, token and risk signal. Captchas can increase the cost of automation but are not reliable protection on their own. Permanent account lockouts can also be abused to block other users. MFA, breached-password checks and monitoring for unusual login behavior provide stronger layers. Penetration tests can verify how these measures work together.