What Is Credential Stuffing?

What Is Credential Stuffing?

Credential stuffing is a type of automated cyberattack where criminals take login credentials typically stolen in a data breach and use them to try to access accounts on other sites. The hacker's assumption here is that you reuse the same username and password with other sites, which also gives them the keys to those accounts as well.

Stolen login credentials are the leading way attackers gain access in security breaches, according to a 2025 Verizon report. In 86% of security breaches of online accounts and platforms, attackers used stolen usernames and passwords to gain access.

For example, an attacker may have thousands or even millions of login credentials stolen from a company where you have an account. Hackers often gain access to these login details from a data breach, phishing, malware or by purchasing on the dark web. They can then test those credentials across other commonly used websites. They're essentially playing the odds that you also have an account at one of those sites and use the same username and password. In that case, these cybercriminals may be able to access that account.

In most cases, these login attempts fail. On average, only about 0.1%, or one out of every 1,000 login attempts, are successful. But these criminals may have millions of login credentials, along with automated tools to test them at scale. That means that despite the low success rate, they can still access thousands of accounts to get sensitive personal information like your financial data.

Credential Stuffing vs. Brute Force Attacks

Credential stuffing and brute force attacks are similar in that both use automated programs to try to break into a high volume of accounts. The way they attempt to gain access, however, is distinctly different.

• Brute force attacks try to guess passwords by running random strings, common patterns, phrases and other variations. Since they don't rely on any stolen data, their success rate is much lower, especially when users choose strong passwords.
• Credential stuffing, on the other hand, uses actual usernames and passwords that hackers have already stolen. Even with a strong password, using it on more than one site could put your accounts at risk.

Tip: While data breaches are commonly associated with large banks, credit card companies and popular shopping sites, they can happen to any of your accounts, even ones you might not expect. For example, hackers could just as easily target the loyalty programs, email platforms and streaming services you use.

How to Protect Yourself From Credential Stuffing

Experian's 2025 U.S. Identity & Fraud Report found that 57% of consumers worry about the security of their online activities, with identity theft, stolen credit card information and online privacy among their top concerns. Credential stuffing is a common method hackers use to break into accounts, but the following steps can help you limit your exposure to it.

• Create strong, unique passwords. Since credential stuffing relies on you using the same login credentials across multiple accounts, the best security step you can take is to create strong passwords you only use once. Use long passwords that mix lowercase and uppercase letters, numbers and symbols.
• Use a password manager. A password manager like 1Password or LastPass can help you create strong passwords and store them securely. Once you set up the app and save your credentials for each site, it can automatically fill them in when you log in.
• Turn on multifactor authentication (MFA). You've probably used MFA before, such as when you log in with your password and then must enter a one-time code you receive via text or email. MFA is optional on many websites, but you should turn it on whenever it's available to add another layer of protection to your accounts.
• Check if your information has been exposed. Data breach notification services like Have I Been Pwned can help you find out if your login details have already been compromised in a data breach. You might also consider getting a free dark web scan with Experian to discover if your Social Security number, email or phone number are available on the dark web. If so, make sure to change your passwords as soon as possible.
• Freeze your credit. If your login info has been compromised and you think your identity could be at risk, you have the right to freeze your credit with the three major credit bureaus (Experian, TransUnion and Equifax). This free protection limits access to your credit report by creditors to prevent someone from opening an account in your name.

Learn more: What Are the Risks of Multifactor Authentication?

What to Do if You're a Victim of Credential Stuffing

Hackers are relentlessly trying to break into user accounts using stolen usernames and passwords. A 2023 Human Defense Platform report shows the security company shielded customers from 26 billion fraudulent login attempts, representing one out of every five login page visits. If you suspect you're a victim of credential stuffing, here are some steps you can take.

• Change your passwords immediately. Start with the affected account, then update any others that use the same login.
• Delete accounts you no longer use. If you haven't used a site or service in a while, consider deleting the account to further limit your exposure to credential stuffing attacks.
• Check your accounts for unauthorized access. Look for unfamiliar logins, purchases or password reset attempts in your accounts. If you see anything out of the ordinary, contact the company's security or fraud department for help securing your profile.
• Watch your financial accounts and credit reports. Keep in mind, credential stuffing attacks can sometimes lead to identity theft. Regularly review your bank and credit card statements, and consider setting up account alerts for suspicious activity.
• File a report if your identity was stolen. Report it to the Federal Trade Commission at IdentityTheft.gov and follow their recovery steps. You can then use the report to support your claims when restoring your affected accounts.

Learn more: Here's What You Should Do After a Data Breach

The Bottom Line

The primary way hackers execute data breaches is by using stolen credentials, often from reused passwords. If you use the same login details across multiple accounts, a credential stuffing attack on one site could also leave these accounts vulnerable to unauthorized access.

While you're securing your accounts, consider taking a moment to strengthen your credit protection. Experian's free credit monitoring service notifies you of changes on your credit report like new accounts, inquiries or updates to your personal information. These alerts may help you catch signs of fraud early and reduce the risk of identity theft and damage to your credit.