Credential Stuffing

Credential Stuffing

What Is Credential Stuffing? 

Credential stuffing is a form of cyber attack where an attacker uses automated tools to test large numbers of stolen or leaked credentials (usernames and passwords) against multiple websites or services, aiming to gain unauthorized access to privileged user accounts. 

This attack method exploits the unfortunate truth that many people reuse the same login credentials across multiple platforms, allowing attackers to gain access to multiple accounts with the same set of compromised credentials.

This is part of a series of articles about insider threat

How Does Credential Stuffing Affect Your Organization? 

Credential stuffing can have significant negative impacts on an organization, including:

  • Unauthorized access to sensitive data: If attackers gain access to employee or customer accounts, they can access sensitive information such as financial data, personal details, and trade secrets, leading to potential data breaches and loss of customer trust.
  • Reputation damage: A successful credential stuffing attack can harm an organization’s reputation, as customers and partners may lose faith in the company’s ability to protect their data.
  • Financial loss: Credential stuffing attacks can lead to direct financial losses through fraudulent transactions, theft of intellectual property, or ransom demands for stolen data. There may also be indirect costs associated with incident response, legal fees, and regulatory fines.
  • Operational disruption: An attacker gaining access to critical systems may disrupt business operations, causing downtime and reduced productivity.
  • Increased workload for IT and security teams: Credential stuffing attacks can create additional work for IT and security personnel — or even outside consultant resources — as they must respond to the incident, investigate its extent, and implement remediation measures.
  • Compliance violations: A successful attack may lead to violations of data protection regulations, such as GDPR or HIPAA, resulting in fines and penalties.

How Does a Credential Stuffing Attack Work? 

A credential stuffing attack typically involves the following steps:

  1. Acquiring credentials: Attackers first obtain a large set of leaked or stolen usernames and passwords, often from data breaches, dark web forums, or through other illicit means.
  2. Preparing the list: The attackers may clean, sort, and organize the credentials to increase the likelihood of successful matches. They may also test the credentials against known breach datasets to remove invalid or expired ones.
  3. Selecting targets: Attackers choose websites or services they want to target, often focusing on popular platforms where users are likely to reuse credentials or have valuable information.
  4. Automation: Attackers use automated tools or scripts, also known as “bots,” to systematically attempt to log in to the targeted websites or services using the acquired credentials. These tools can often bypass basic security measures like CAPTCHAs and can distribute the login attempts across multiple IP addresses to evade detection.
  5. Identifying successful logins: The automated tools record successful logins, and attackers gain access to the compromised accounts.
  6. Exploiting the accounts: Once they have access, attackers may exploit the accounts for various purposes, such as stealing sensitive data, making fraudulent purchases, spreading malware, or launching further attacks.

Credential Stuffing vs. Brute Force Attacks vs. ATO (Account Takeovers) 

Credential stuffing, brute force attacks, and account takeovers (ATO) are all methods used by attackers to gain unauthorized access to privileged accounts, but they differ in their approach and techniques, as detailed in the following table.

Attack TypeDefinition and TechniquesEfficiencyDetection and Mitigation StrategiesUser Protection Strategies
Credential StuffingUsing leaked or stolen credentials from one data breach to access a user’s accounts on unrelated websites and services. Automated tools are used to test these credentials on various platforms.Relies on users reusing the same username and password across multiple accounts.Monitoring for failed login attempts, IP address analysis, and rate limiting. Encouraging users to utilize unique, strong passwords and enable multi-factor authentication (MFA).Unique, strong passwords; MFA.
Brute Force AttacksSystematically guessing a user’s password by attempting numerous combinations until the correct one is found. Does not rely on previously leaked credentials but instead on exhaustive search techniques.Less efficient than credential stuffing.Monitoring for repetitive login attempts, implementing account lockouts or delays after a specified number of failed attempts, MFA, and using CAPTCHAs.Strong, complex passwords, setting MFA where possible.
Account TakeoversUnauthorized access and control of a user’s account, which may be achieved through credential stuffing, brute force attacks, or other means like phishing or social engineering.Depends on the specific method employed.Monitoring for unusual account activity, using behavior analytics to identify potential account compromises, and employing strong authentication mechanisms such as MFA.Strong passwords; MFA; awareness.

How to Detect and Prevent Credential Stuffing 

Detecting and preventing credential stuffing exploits is essential to protect user accounts and sensitive data. Here are some effective strategies

Multi-Factor Authentication (MFA)

MFA introduces an extra layer of security by requiring users to submit more than one form of identification when logging in. Commonly, this involves a combination of something the user knows (e.g., a password or pattern), something the user has (e.g., a physical token or mobile device), and/or something the user is, (e.g., a fingerprint or facial recognition). MFA makes it significantly more difficult for attackers to access target accounts, even if they know the correct password.

Device Fingerprinting

Device fingerprinting involves collecting unique characteristics of a user’s device, such as browser type, operating system, or installed plugins. This information can help identify suspicious login attempts from unfamiliar devices. By comparing the fingerprint of the device used in a login attempt to known legitimate devices, organizations can flag and block potential credential stuffing attacks.

IP Allow Listing

IP allow listing involves blocking or restricting access from known malicious IP addresses or IP ranges. By monitoring and analyzing failed login attempts, organizations can identify IP addresses that show patterns indicative of credential stuffing attacks and prevent future attempts from those sources.


CAPTCHAs are tests designed to differentiate between human users and automated bots. By requiring users to complete a CAPTCHA challenge during the login process, organizations can make it more difficult for attackers to use automated tools for credential stuffing. However, advanced bots can sometimes bypass CAPTCHAs, so this should not be the sole defense mechanism.

Enforce Active Directory Auditing for Strong Passwords 

Promoting good password hygiene among employees is crucial to reduce the risk of credential stuffing attacks. However, it is also important to implement Active Directory (AD) auditing to ensure that everyone is using strong, secure passwords. Organizations should verify that users are creating strong, unique passwords, while not reusing passwords across multiple accounts. Password managers can also help employees maintain secure credentials.

Enforce Password Hygiene 

Enforcing password hygiene involves implementing policies and practices that promote the creation and management of strong, secure passwords. Key practices include:

  • Enforce history: Prevent users from reusing previous passwords by maintaining a password history and restricting the reuse of recent passwords.
  • Set maximum password ages: Require users to change their passwords periodically by setting a maximum password age, such as 60 or 90 days.
  • Set length and complexity requirements: Ensure passwords are strong by requiring a minimum length (NIST recommends a minimum 8 digits for user-chosen passwords, with 14-16 characters are accepted as the strongest), with a mix of uppercase and lowercase letters, numbers, and special characters.
  • Limit session times: Reduce the risk of unauthorized access by automatically logging users out after a set period of inactivity and limiting the duration of sessions.
  • Use access management policies: Implement Privileged Access Management (PAM) or specific policies for administrator and service accounts, ensuring they follow stricter password and access control requirements.
  • Enable password expiration alerts: Send notifications or emails to users reminding them to update their passwords before they expire, helping to maintain password hygiene and avoid account lockouts.

Learn more in our detailed guide to detecting insider threats

Detecting Credential Stuffing with Exabeam

Threat Detection, Investigation, and Response (TDIR) use case categories is an outcome-based framework for using Exabeam products. It describes what threat you can detect, investigate, hunt, and respond to using a prescribed end-to-end workflow. 

The TDIR categories framework organizes threats in a hierarchy so you can break them down from a general type, like Compromised Insiders, to a specific scenario, like Brute Force Attack or Compromised Credentials. There are three overarching use case categories: Compromised Insiders, Malicious Insiders, and External Threats.

Outcomes Navigator for Exabeam Security Log Management and Exabeam SIEM shows you whether you have the right log sources and fields parsed within the use case categories to get a complete view of a credential stuffing or brute force attack. Then you can see whether you have specific Correlation Rules set up to create alerts of interest, as well as Dashboards for visualization of potential events and attacks. 

If you have Exabeam Fusion, Exabeam Security Investigation, or Exabeam Security Analytics, you will additionally see which analytics rules cover credential-based attacks like credential stuffing, brute force, or account takeovers.

Learn more: Exabeam UEBA