Credential Stuffing

Credential stuffing exploits password reuse—when users use the same credentials across multiple sites, a breach at one service compromises accounts everywhere.

How credential stuffing works

1. Attackers obtain credential lists from data breaches (often sold on dark web).
2. Automated tools test these credentials against target login pages at scale.
3. Successful logins grant access to accounts, payment methods, and personal data.
4. Compromised accounts are used for fraud, identity theft, or sold to other criminals.

Why it's effective

• 65% of users reuse passwords across multiple accounts.
• Billions of leaked credentials are freely available.
• Automated tools can test millions of combinations quickly.
• Many sites lack adequate bot detection or rate limiting.

Defense strategies

• Implement multi-factor authentication (MFA) to block password-only access.
• Deploy bot detection and CAPTCHA on login forms.
• Use rate limiting to slow automated login attempts.
• Monitor for credential leaks using breach notification services.
• Enforce strong, unique passwords via password policies.
• Check passwords against known breach databases (like Have I Been Pwned).
• Implement account lockout after failed attempts.