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Home/Glossary/Credential Stuffing
Glossary · Attack Vector

What Is Credential Stuffing?

An automated cyberattack where stolen username and password combinations from data breaches are systematically tested against other websites and services to gain unauthorized access to accounts where users reused the same credentials.

Quick Definition

An automated cyberattack where stolen username and password combinations from data breaches are systematically tested against other websites and services to gain unauthorized access to accounts where users reused the same credentials.

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01Credential Stuffing explained.

Credential stuffing exploits one of the most common security mistakes: password reuse. When a data breach exposes millions of email/password combinations, attackers use automated tools to test those credentials against hundreds of other websites, knowing that many people use the same password everywhere.

Billions of stolen credentials are available on the dark web from breaches at major companies. Automated tools can test thousands of login combinations per second, making credential stuffing attacks both cheap and effective.

Unlike brute force attacks that try random passwords, credential stuffing uses real credentials that actually worked on other sites. This makes it far more effective and harder to detect, as each login attempt uses a legitimate-looking username and password.

02How it works.

01Attackers obtain large databases of stolen credentials from data breaches (available on the dark web)
02Automated tools test each username/password pair against target websites (banks, email, shopping)
03When a login succeeds, the attacker has confirmed the user reused their password
04Compromised accounts are used for fraud, identity theft, or sold to other criminals
05The attack is distributed across many IP addresses to avoid detection

03Real-world example.

In 2020, over 500,000 Zoom account credentials were found for sale on the dark web for less than a penny each. They were obtained through credential stuffing, not a Zoom breach — users had reused passwords from other compromised services.

04How to protect yourself.

01Use a unique password for every single account — a password manager makes this easy
02Enable two-factor authentication on all accounts that support it
03Check haveibeenpwned.com to see if your credentials have been exposed in a breach
04Change passwords immediately for any account where you reused a breached password
05Use passkeys or hardware security keys where available
Related Terms
Brute Force AttackIdentity TheftTwo-Factor Authentication (2FA)
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