What is Credential Stuffing?

Credential stuffing is one of the most common and effective attack methods used today. It's not sophisticated hacking—it's simply using passwords stolen from one breach to break into accounts on other services. And it works because most people reuse passwords.

How Credential Stuffing Works

When a company suffers a data breach, user credentials often end up for sale on underground forums. Attackers purchase these lists—sometimes containing millions of email and password combinations—and use automated tools to test them against other websites.

These tools can attempt thousands of logins per minute across multiple services simultaneously. If you used the same password for a gaming forum that got hacked and your bank account, attackers will find that match quickly.

Why It's So Effective

Studies consistently show that over 60% of people reuse passwords across multiple accounts. Some use the same password everywhere. This behavior turns a single breach into a skeleton key that unlocks accounts across the entire internet.

Even partial password reuse is dangerous. Attackers know common patterns—adding numbers to the end, capitalizing the first letter, or swapping letters for numbers. Their tools account for these variations.

The Scale of the Problem

Credential stuffing attacks happen constantly. Major websites report blocking millions of malicious login attempts every day. But not every attack is caught, and not every company has robust defenses.

The success rate for credential stuffing is typically 0.1% to 2%. That might sound low, but when attackers are testing millions of credentials, those small percentages translate to thousands of compromised accounts.

What Attackers Do Next

Once inside an account, attackers have options. They might steal stored payment information, make fraudulent purchases, access sensitive documents, or use the account as a stepping stone to other services.

Email accounts are especially valuable—they're often used for password resets on other services. Compromising someone's email can give attackers the ability to take over every other account that person owns.

How to Protect Yourself

• Use unique passwords — Every account should have its own password. A password manager makes this practical.
• Enable two-factor authentication — Even if attackers have your password, they can't get in without the second factor.
• Check for breaches — Regularly search for your credentials in breach databases so you know when to change passwords.
• Monitor account activity — Enable login notifications where available so you know immediately if someone else accesses your account.