What Is Credential Stuffing?
Credential stuffing is a cyberattack method in which attackers use lists of compromised user credentials to breach into a system. The attack uses bots for automation and scale and is based on the assumption that many users reuse usernames and passwords across multiple services.
Credentials are often obtained from data breaches and are tested en masse to exploit users who reuse the same passwords across multiple sites. By automating the process, attackers can quickly determine which credentials are still valid, gaining unauthorized access to user accounts with minimal effort.
Unlike targeted attacks, credential stuffing leverages the volume of available breached credentials and the common behavior of password reuse. Attackers focus on scale, not on a specific individual. If even a small percentage of attempted logins succeed, attackers can compromise thousands of accounts.
The consequences for users and companies can include unauthorized purchases, drained financial accounts, and exposure of sensitive information. Successful credential stuffing also often leads to further breaches as attackers pivot to additional services linked to compromised accounts.
This is part of a series of articles about website security
In this article:
- Credential Stuffing vs. Brute Force Attacks
- Anatomy of a Credential Stuffing Attack
- Real-World Examples of Credential Stuffing Attacks
- Best Practices for Credential Stuffing Attacks Prevention and Mitigation
Credential Stuffing vs. Brute Force Attacks
Credential stuffing and brute force attacks are both methods for gaining unauthorized access to user accounts, but they differ significantly in technique and intent.
In credential stuffing, attackers use known username-password pairs—typically sourced from previous data breaches—and attempt to log into other services where users might have reused the same credentials. It’s a volume-based attack that relies on automation and the probability of password reuse across sites.
Brute force attacks involve systematically guessing passwords for a single account. The attacker tries many possible combinations—either randomly or using a dictionary of common passwords—until they succeed. This method doesn’t rely on previously leaked credentials but instead exploits weak or simple passwords.
Credential stuffing is faster and more efficient because it uses real-world, already-compromised credentials. Brute force attacks are slower and more easily detected due to the high volume of failed attempts on a single account.
Anatomy of a Credential Stuffing Attack
A credential stuffing attack typically unfolds in several stages, each enabled by automation and access to breached data.
- Acquisition of credentials: Attackers start by obtaining large sets of username-password pairs from publicly available data breaches, dark web marketplaces, or private leak forums. These datasets often contain millions of entries and are aggregated into credential lists known as “combo lists.”
- Preparation and tooling: Next, attackers configure automated tools such as Sentry MBA, Snipr, or OpenBullet. These tools rapidly test credentials against login pages. Configuration files (configs) for each target service are often shared within attacker communities to streamline the process.
- Credential testing: Using the tools and configs, attackers launch login attempts across the target site. This stage involves sending a high volume of requests, typically through proxies or botnets to avoid IP blocking and detection. Captchas and rate limits are bypassed using third-party services or scripts.
- Validation and sorting: Once valid credentials are found, the tools log successful matches. These are sorted and stored for further exploitation. Attackers may sell or trade the verified credentials or use them directly to access sensitive data, perform fraudulent transactions, or pivot to other accounts.
- Post-exploitation: Compromised accounts can be monetized in various ways. For example, attackers may steal personal data, redeem stored value or points, or use access to launch phishing or social engineering attacks. In corporate environments, they may attempt lateral movement to access internal systems.
Defenders must understand each of these steps to effectively detect and mitigate credential stuffing attempts before damage occurs.
Related content: Read our guides to phishing attack and session hijacking
Real-World Examples of Credential Stuffing Attacks
Here are a few real‑world examples of credential stuffing attacks that highlight how widespread and damaging this threat has become:
1. The North Face / VF Corporation — April 2025
On April 23, 2025, The North Face website was targeted by a credential stuffing campaign using previously leaked credentials. The attacker gained access to customer accounts and exposed data, including names, email addresses, shipping addresses, phone numbers, purchase history, and dates of birth. No payment card data was compromised, as the company uses third‑party processors. This is the fourth credential stuffing incident affecting VF Corporation brands since 2020.
2. Australian Superannuation Funds — March 2025
Multiple funds—including AustralianSuper, Rest Super, Hostplus, Australian Retirement Trust, and Insignia Financial—detected coordinated credential stuffing attempts over March 29–30, 2025. Although most funds repelled the attacks, some members of AustralianSuper lost a combined AUD 500,000, and approximately 8,000 Rest Super members had personal data accessed. The incident prompted regulatory scrutiny and reinforced calls for stronger MFA beyond SMS-based methods.
3. 23andMe — October 2023 Breach (Expanded via Credential Stuffing)
In October 2023, a threat actor used a credential stuffing approach—replaying reused credentials from prior leaks—to access the DNA Relatives feature. This compromised approximately 5.5 million user profiles, even though the initial credential reuse involved only ~14,000 accounts. The incident triggered password resets and the introduction of two‑step verification across the platform.
4. PayPal — December 2022 / Early 2023
PayPal disclosed that between December 6–8, 2022, nearly 35,000 customer accounts were accessed via credential stuffing. Exposed data included names, addresses, dates of birth, social security numbers, and tax ID.
Broader Trends and Observations
Security firms reported surging credential stuffing activity in mid‑2025, with multiple retailer and cloud‑based platforms targeted by automated attack tools leveraging breached credentials from unrelated leaks. Over 100 threat scripts published between late 2024 and mid‑2025 showed trends like business‑logic manipulation and API exploitation built into modern credential stuffing campaigns.
Sources: Daily Security Review, Holthouse et al., 2025, Cybersecurity Dive, ForceNow
Best Practices for Credential Stuffing Attacks Prevention and Mitigation
Implement Browser Security Measures
Web applications can reduce the success of credential stuffing attacks by implementing browser-based security features that disrupt automated login attempts. Techniques like enforcing CAPTCHA challenges, browser fingerprinting, and JavaScript-based interaction checks can help distinguish between human users and bots. These measures increase the cost and complexity for attackers, making large-scale automated attempts less effective.
Session and cookie management also play a role. Configuring short-lived session tokens, enforcing secure cookies, and monitoring for unusual session reuse can prevent attackers from reusing valid login sessions obtained through automation. Adding protections such as Content Security Policy (CSP) and SameSite cookie attributes can further reduce the attack surface by limiting how credentials and tokens are exposed in the browser.
Finally, organizations should adopt rate limiting and login throttling mechanisms at the browser interaction level. By restricting the number of failed login attempts per user, device, or IP, they can make automated credential stuffing attempts slower and easier to detect, while still preserving a smooth experience for legitimate users.
Implement Strong Password Policies
Organizations need to enforce strong password requirements that prevent users from setting simple, easy-to-guess passwords. These policies should require a minimum length and a mix of character types, and must prohibit commonly used passwords and credentials previously exposed in breaches. Implementing tools that automatically check password strength and prevent the use of compromised passwords during account registration or password changes can significantly reduce risk.
Equally important is educating users about password hygiene. Encouraging the use of unique passwords for each service and recommending password managers reduces the likelihood that a breach on one platform can endanger accounts on others.
Learn more in our detailed guide to browser security
Implement Multi-Factor Authentication
Multi-factor authentication (MFA) adds a layer of defense by requiring users to provide an additional verification step beyond a password. Even if attackers obtain valid credentials, MFA can prevent unauthorized access since the second factor—such as a one-time code sent to the user’s phone—is typically harder to compromise. Organizations should deploy MFA across all sensitive and user-facing systems, making it a default rather than an optional feature.
Providing diverse MFA methods, such as app-based authenticators, hardware tokens, or biometrics, can improve usability and adoption rates. Administrators must also ensure there are processes in place to handle lost devices and MFA resets securely, as these can be targeted by attackers as alternative avenues for compromise.
Bot Detection and Anomaly Analysis
Credential stuffing attacks rely on bots to perform high volumes of login attempts. Utilizing bot detection solutions, such as device fingerprinting, browser behavior analysis, and machine learning-trained anomaly detection, enables organizations to distinguish between human users and automated traffic. Blocking or rate-limiting suspicious login activity based on such analysis is essential for reducing the success rate of these attacks.
Anomaly analysis can also detect subtle variations in login behavior, such as unusual access locations, odd sign-in times, or simultaneous logins from multiple IPs. Alerting and automatic intervention—such as triggering additional verification or account lockout—can help prevent attackers from leveraging even the valid credentials that slip through initial defenses.
Conduct Continuous Training
Continuous security training for both employees and users helps reduce the risk of credential stuffing by raising awareness about secure behaviors and new attack trends. Employees responsible for access management must understand how credential stuffing works, its early warning signs, and the importance of timely reporting of suspicious activity. Regular training reinforces organizational policies and the critical nature of prompt action when attacks are detected.
User education is also important; organizations should routinely remind users about password best practices, the dangers of reusing credentials, and the benefits of enabling multi-factor authentication. Phishing simulations, security alerts, and educational campaigns can help users recognize and respond safely to potential threats.
Threat Intelligence and Leakage Detection
Threat intelligence platforms can monitor dark web forums, paste sites, and other sources for emerging credential breaches involving an organization’s users or domains. Early detection of leaked credentials enables rapid response—such as resetting passwords, forcibly logging out users, or warning affected individuals—before widespread exploitation occurs. Integrating threat intelligence feeds into security operations provides both proactive and reactive defense capabilities.
Additionally, deploying dedicated credential leakage detection solutions, such as identity protection services or browser plugins, can notify users when their credentials are found in known breaches. These tools empower both organizations and users to remediate risks quickly, limiting the damage from data leaks and reducing the window of opportunity for attackers leveraging exposed credentials. Regularly updating and refining these detection mechanisms is necessary to keep pace with the evolving tactics of cybercriminals.
Preventing Credential Stuffing with Seraphic Security
Organizations looking to eliminate the risk of credential stuffing attacks are turning to Seraphic’s Secure Enterprise Browser (SEB) for proactive protection. Seraphic is purpose-built for enterprise security, embedding advanced bot mitigation, robust session management, and real-time credential monitoring directly into the browser experience. By automatically identifying and blocking automated login attempts, Seraphic ensures that even sophisticated credential stuffing campaigns are stopped at the entry point, while legitimate user access remains seamless.
In addition, Seraphic integrates threat intelligence and live credential leakage detection within its browser framework. This enables organizations to receive instant alerts when compromised credentials are detected or used, empowering rapid response and password resets before accounts can be abused. Combined with enforced browser-based MFA and strong, policy-driven password controls, Seraphic provides a layered defense that neutralizes the main attack vectors exploited in credential stuffing campaigns. With Seraphic, companies gain peace of mind through continuous browser security tailored to the needs and risks of the modern, distributed workforce.
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