A credential stuffing attack is a type of cyberattack where criminals take usernames and passwords stolen from one site and automatically try them on many other sites to hijack accounts. It succeeds because many people reuse the same login credentials across multiple services.

What it is

Credential stuffing is an automated injection of stolen username–password pairs into login forms to gain unauthorized access to user accounts. Unlike classic brute force, attackers are not guessing passwords; they are reusing real, previously leaked credentials.

How a credential stuffing attack works

  • Attackers obtain large lists of breached credentials from data leaks or dark‑web marketplaces.
  • They use botnets or other automation tools to try those logins at scale against many websites and apps.
  • When a login works on a new site, the account is effectively taken over and flagged for further abuse.

Why it’s dangerous now

  • Billions of credentials from past breaches are widely available, making these attacks cheap and common.
  • Modern tools imitate human behavior (random delays, realistic mouse moves, residential IPs) to evade simple bot defenses.
  • Successful attacks can lead to fraud, identity theft, data theft, and resale of “verified” accounts on underground markets.

How to protect yourself

  • Use unique passwords for every account, ideally generated and stored by a password manager.
  • Turn on multi‑factor authentication (MFA) wherever possible so stolen passwords alone are not enough.
  • Watch for unusual login alerts and quickly change passwords if a service reports a breach or suspicious activity.

TL;DR: Credential stuffing is when attackers reuse real, stolen logins from one site to break into your other accounts using large‑scale automation; unique passwords plus MFA are the best defenses.

Information gathered from public forums or data available on the internet and portrayed here.