Credential Stuffing

Definition of Credential Stuffing

Credential stuffing is a cyber attack technique in which attackers use automated tools to test large sets of stolen login credentials on various websites, hoping to gain unauthorized access to user accounts. This method capitalizes on the fact that many people reuse the same usernames and passwords across multiple platforms. To protect themselves, users are encouraged to utilize unique and complex passwords for each of their accounts.


The phonetic pronunciation of the keyword “Credential Stuffing” is: C-R-E-D-E-N-T-I-A-L / S-T-U-F-F-I-N-G/krɪˈdɛnʃəl/ /ˈstʌfɪŋ/

Key Takeaways

  1. Credential stuffing is an automated cyber attack where hackers use stolen login credentials from one data breach to gain unauthorized access to other accounts, exploiting the widespread reuse of the same usernames and passwords.
  2. The most effective way to defend against credential stuffing attacks is to implement strong security practices such as using unique and complex passwords for each online account, enabling multi-factor authentication (MFA), and monitoring accounts for any suspicious activity.
  3. Organizations must also actively combat credential stuffing attacks by implementing security measures like rate limiting, CAPTCHAs, and IP address tracking, as well as monitoring the internet for leaked credentials and prompting affected users to update their passwords.

Importance of Credential Stuffing

Credential stuffing is an important technology term because it refers to a prevalent cyber attack method where criminals use automated tools to test a large number of stolen access credentials (like usernames and passwords) on multiple websites, hoping to find ones that work across different platforms.

This type of attack capitalizes on users’ tendency to reuse passwords for multiple accounts, posing a significant security risk for both individuals and organizations.

By breaching an account, cybercriminals can access sensitive data, conduct identity theft, tamper with systems, or spread malware.

Understanding and addressing the issue of credential stuffing is crucial in creating robust security measures and promoting practices such as strong, unique passwords and multi-factor authentication in order to prevent unauthorized access and safeguard valuable information.


Credential stuffing is a cyberattack method commonly used by hackers to gain unauthorized access to various online platforms and user accounts, primarily for the purpose of fraud and data theft. This practice capitalizes on the tendency of internet users to reuse the same passwords and usernames across multiple services. The attackers exploit massive databases of breached user credentials, often amassed through prior data breaches and hacks on other platforms, and then employ automated tools to test these credentials on multiple sites in an attempt to gain access to user accounts on other platforms.

By successfully “stuffing” a platform with previously compromised credentials, the attacker can access personal information, perform fraudulent transactions or, in certain cases, manipulate the affected system to their advantage. The significance of credential stuffing lies in its wide-ranging implications for online security and privacy. It poses a considerable risk to individuals and businesses alike, resulting in unauthorized access to sensitive personal and company information, financial losses, and reputational damage.

To mitigate these risks, it is crucial for organizations to implement effective security measures, such as multi-factor authentication, continuous monitoring of login activities, and regular password resets for users. Furthermore, individuals are encouraged to adopt better password management habits, such as using unique and complex passwords for each online account and employing password managers to secure their login credentials. By taking these proactive steps, users and organizations can significantly reduce the effectiveness of credential stuffing attacks and safeguard their valuable digital assets.

Examples of Credential Stuffing

2018 Reddit Breach: In August 2018, Reddit reported a security breach in which hackers had accessed user information, including hashed passwords, email addresses, and private messages. The attack was a result of credential stuffing, where the threat actors had logged in using stolen credentials of some Reddit employees, bypassing SMS-based two-factor authentication. As a precaution, Reddit notified affected users and required them to change their passwords.

2017 Uber Data Breach: In 2017, Uber revealed that it had suffered a massive data breach in 2016, affecting nearly 57 million users and drivers. Credential stuffing was one of the factors that contributed to this breach. Attackers reused valid login credentials gleaned from an unrelated data breach to gain unauthorized access to Uber’s user accounts and internal systems, which contained user names, phone numbers, email addresses, and drivers’ license details of millions of users.

2020 Zoom Security Issues: With the sudden increase in remote work in 2020, the use of video conferencing platform Zoom surged exponentially. During this period, Zoom faced a series of security issues, including “Zoombombing,” where uninvited guests joined meetings. One of the contributing factors to these issues was credential stuffing. Around 500,000 stolen Zoom usernames and passwords were reportedly being sold or offered for free on the dark web, allowing cybercriminals to join meetings without a formal invitation. As a response, Zoom took necessary steps to strengthen its security and introduced additional features to prevent these incidents from happening.

FAQ: Credential Stuffing

What is credential stuffing?

Credential stuffing is a type of cyberattack where attackers use automated tools to inject stolen usernames and passwords into various websites to gain unauthorized access to user accounts. This type of attack takes advantage of the fact that many people reuse the same login credentials across multiple sites.

How does credential stuffing work?

Attackers begin by compiling large databases of login credentials that have been leaked through data breaches or obtained through other means, such as phishing. They then use custom-built software or existing tools, like botnets, to systematically attempt to log in to various websites and services using these credentials. If a login attempt is successful, they can gain unauthorized access to sensitive information or even steal the victim’s identity.

How can I prevent credential stuffing attacks?

To protect against credential stuffing attacks, follow these best practices:

  • Use unique and strong passwords for each account.
  • Enable multi-factor authentication (MFA) whenever available.
  • Monitor your accounts for suspicious activity and respond quickly.
  • Regularly update and change your passwords.
  • Be cautious about phishing attempts and do not share your credentials.

What are some common signs of a credential stuffing attack?

Common indications of a credential stuffing attack may include:

  • Unexpected account lockouts due to multiple failed login attempts.
  • Unauthorized access to your accounts or unauthorized changes to your personal information.
  • Emails or notifications about suspicious activity on your accounts.
  • An increase in spam or phishing email messages.

What should I do if I become a victim of credential stuffing?

If you suspect you are a victim of credential stuffing, take the following steps:

  • Immediately change the passwords for the affected accounts and any accounts using the same credentials.
  • Enable multi-factor authentication (MFA) on any accounts that support it.
  • Monitor your financial and credit activity for unauthorized transactions and report them immediately.
  • Contact the website or service provider where your credentials were compromised to report the breach.
  • Be vigilant in watching for phishing attempts and other signs of continued unauthorized access.

Related Technology Terms

  • Brute Force Attack
  • Account Takeover (ATO)
  • Password Spraying
  • Two-Factor Authentication (2FA)
  • Data Breach

Sources for More Information


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