Credential stuffing is a cyberattack where hackers use stolen usernames and passwords from data breaches to try and gain access to multiple accounts. Since many people reuse passwords across different platforms, attackers can use automated bots to test stolen credentials on multiple sites, including:

Bank accounts
Social media profiles
Email accounts
E-commerce websites
If the victim has reused their password, the hacker can take over accounts, steal sensitive data, and even make fraudulent transactions.

How Does This Happen?
1. Data Breaches and Leaked Passwords
Hackers obtain stolen credentials from previous data breaches (e.g., leaked user databases from Facebook, LinkedIn, or Dropbox).
These credentials are sold on the dark web or used by cybercriminals directly.
2. Automated Bots Test Stolen Credentials
Attackers use credential stuffing tools to quickly test usernames and passwords on multiple platforms.
If a match is found, the hacker gains access and takes control of the account.
3. Account Takeovers and Financial Fraud
Once inside, the hacker can:
Steal personal and financial data
Change account details to lock out the victim
Make unauthorized purchases or withdrawals

Example of a Credential Stuffing Scam
Lisa, a frequent online shopper, uses the same password for her Amazon, PayPal, and Gmail accounts. A hacker buys stolen credentials from a recent data breach and runs a credential stuffing attack.

Since Lisa’s password was exposed, the hacker:

Logs into her PayPal account and transfers money.
Changes her Amazon password and places fraudulent orders.
Accesses her Gmail and resets passwords for other services.

How to Protect Yourself from Credential Stuffing
1. Use Unique Passwords for Every Account
Never reuse the same password across different websites.
Use a password manager to generate and store unique passwords.
2. Enable Two-Factor Authentication (2FA)
Even if hackers steal your password, they won’t be able to access your account without a second verification step.
Use an authenticator app instead of SMS for better security.
3. Monitor Your Accounts for Suspicious Activity
Check login history on important accounts like email and banking.
Use services like Have I Been Pwned to check if your credentials have been leaked.