What Is Credential Stuffing?

What Is Credential Stuffing?

Here we can see, “What Is Credential Stuffing?”

What Is Credential Stuffing?

Credential stuffing may be a cyberattack method during which attackers use lists of compromised user credentials to breach a system. The attack uses bots for automation and scale and is predicated on the idea that many users reuse usernames and passwords across multiple services. Statistics show that about 0.1% of breached credentials attempted on another service will end in a successful login.

Credential stuffing may be a rising threat vector for 2 main reasons:

  • The broad availability of massive databases of breach credentials, such as “Collection #1-5,” made 22 billion username and password combinations openly available in plaintext to the hacker community.
  • More sophisticated bots that simultaneously attempt several logins and appear to originate from different IP addresses. These bots can often circumvent simple security measures like banning IP addresses with too many failed logins.

It Starts With Leaked Password Databases

Attacks against online services are common, and criminals often exploit security flaws in systems to accumulate databases of usernames and passwords. Databases of stolen login credentials are often sold online on the dark web, with criminals paying in Bitcoin for the privilege of accessing the database.

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Let’s say you had an account on the Avast forum, which was breached back in 2014. That account was breached, and criminals may have your username and password on the Avast forum. Avast contacted you and had you modify your forum password, so what’s the problem?

Unfortunately, the matter is that a lot of people reuse equivalent passwords on different websites. Let’s say your Avast forum login details were “you@example.com” and “AmazingPassword.” If you log into other websites with an equivalent username (your email address) and password, any criminal who acquires your leaked passwords can access those other accounts.

How Credential Stuffing Attacks Work

Here may be a typical process followed by an attacker during a large-scale credential stuffing attack. The attacker:

  1. Sets up a bot that’s ready to automatically log into multiple user accounts in parallel while faking different IP addresses.
  2. Runs an automatic process to see if stolen credentials work on many websites by running the method parallel across multiple sites, reducing the necessity to log into one service repeatedly.
  3. Monitors successful logins and obtains personally identifiable information, credit cards, or other valuable data from the compromised accounts.
  4. Retains account information for future use, for instance, phishing attacks or other transactions enabled by the compromised service.

How to Protect Yourself

Protecting yourself from credential stuffing is pretty simple and involves following equivalent password security practices security experts have been recommending for years. There’s no magic solution—just good password hygiene. Here’s the advice:

  • Avoid Reusing Passwords: Use a singular password for every account you employ online. That way, albeit your password leaks, it can’t be wont to check in to other websites. Attackers can attempt to stuff your credentials into other login forms, but they won’t work.
  • Use a Password Manager: Remembering strong, unique passwords may be a nearly impossible task if you’ve got accounts on quite a few websites, and almost everyone does. We recommend employing a password manager like 1Password (paid) or Bitwarden (free and open-source) to recollect your passwords for you, and it can even generate those strong passwords from scratch.
  • Enable Two-Factor Authentication: With two-step authentication, you’ve got to supply something else—like a code generated by an app or sent to you via SMS—each time you log in to an internet site. Albeit an attacker has your username and password, they won’t be ready to check in to your account if they don’t have that code.
  • Get Leaked Password Notifications: With a service like Have, I Been Pwned? You’ll get a notification when your credentials appear during a leak.

How Services Can Protect Against Credential Stuffing

While individuals got to take responsibility for securing their accounts, online services have some ways to guard against credential-stuffing attacks.

  • Scan Leaked Databases for User Passwords: Facebook and Netflix have scanned leaked databases for passwords, cross-referencing them against login credentials on their services. If there’s a match, Facebook or Netflix can prompt their user to vary their password. This is often how of beating credential-stuffers to the punch.
  • Offer Two-Factor Authentication: Users should be ready to enable two-factor authentication to secure their online accounts. Particularly sensitive services can make this mandatory, and they will even have a user click a login verification link in an email to verify the login request.
  • Require a CAPTCHA: If a login attempt looks strange, a service can require entering a CAPTCHA code displayed in a picture or clicking through another form to verify that a human— not a bot—is attempting to check in.
  • Limit Repeated Login Attempts: Services should plan to block bots from attempting an outsized number of sign-in attempts during a short period of your time. Modern, sophisticated bots may plan to check in from multiple IP addresses directly to disguise their credential-stuffing attempts.
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Poor password practices—and, to be fair, poorly secured online systems that are often too easy to compromise—make credential stuffing a significant danger to online account security. It’s no wonder many companies within the tech industry want to create a safer world without passwords.

Credential Stuffing Prevention

The following measures can assist you in protecting your website from credential stuffing attacks.

Multi-Factor Authentication (MFA)

Requiring users to authenticate with something they need, additionally to something they know, is that the best defense against credential stuffing. Attacker bots won’t be ready to provide a physical authentication method, like a mobile or access token. In many cases, it’s not feasible to need multi-factor authentication for a whole user base. It is often combined with other techniques; for instance, MFA is often applied only with device fingerprinting.


CAPTCHA, which needs users to act to prove they’re human, can reduce the effectiveness of credential stuffing. However, hackers can easily bypass CAPTCHA by using headless browsers. Like MFA, CAPTCHA is often combined with other methods and applied only in specific scenarios.

Device Fingerprinting

You can use JavaScript to gather information about user devices and make a “fingerprint” for every incoming session. The fingerprint may be a combination of parameters like OS, language, browser, time zone, user agent, etc. If an equivalent combination of parameters is logged in several times in sequence, it’s likely a brute force or credential stuffing attack.

If you employ a strict fingerprint with multiple parameters, you’ll enforce more severe measures, like banning the IP. To capture more attacks, you’ll use a mixture of 2-3 common parameters and enforce less severe measures, sort of a temporary ban. a standard fingerprint combination is an OS + Geolocation + Language.

IP Blacklisting

Attackers will typically have a limited pool of IP addresses, so another effective defense is to dam or sandbox IPs that plan to log into multiple accounts. You’ll monitor the last several IPs that were wont to log into a selected account and compare them to the suspected bad IP to scale back false positives.

Rate-Limit Non-Residential Traffic Sources

It is easy to spot traffic originating from Amazon Web Services or other commercial data centers. This traffic is nearly certainly bot traffic and will be treated far more carefully than regular user traffic. Apply strict rate limits and block or ban IPs with suspicious behavior.

Block Headless Browsers

Headless browsers like PhantomJS are often easily identified by the JavaScript calls they use. Block access to headless browsers because they’re not legitimate users and almost certainly indicate suspicious behavior.

Disallow Email Addresses as User IDs

Credential stuffing relies on the reuse of equivalent usernames or account IDs across services. This is often far more likely to happen if the ID is an email address. By preventing users from using their email address as an account ID, you dramatically reduce the prospect of them reusing an equivalent user/password pair on another site.

Credential Stuffing vs. Brute Force Attacks

Credential stuffing is analogous to a brute force attack, but there are several important differences:

  • Brute force attacks attempt to guess credentials with no context, using random strings, commonly used password patterns, or dictionaries of common phrases
  • Brute force attacks succeed if users choose simple, guessable passwords
  • Brute force attacks lack context and data from previous breaches, and then their login success rate is far lower

In a modern web application with basic security measures in situ, brute force attacks are likely to fail, while credential stuffing attacks can succeed. The rationale is that, albeit you enforce strong passwords, users may share that password across services, resulting in a compromise.


I hope you found this guide useful. If you’ve got any questions or comments, don’t hesitate to use the shape below. 

User Questions:

  1. Why is it called credential stuffing?

Credential stuffing is that the automated injection of stolen username and password pairs (“credentials”) into website login forms to gain access to user accounts fraudulently. … Credential Stuffing typically refers to specifically using known (breached) username/password pairs against other websites.

  1. Is credential stuffing illegal?

Credential stuffing may be a sort of cyber-attack where a taken account’s credentials, usually containing the lists of usernames and email ID alongside the matching passwords, are stolen then wont to gain illegal access to real user accounts over a large-scale automated login.

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  1. What are cyber intruders?

A network intrusion refers to any unauthorized activity on a digital network. Network intrusions often involve stealing valuable network resources and nearly always jeopardize the safety of networks and/or their data.

  1. Ongoing credential stuffing attack – the way to tackle?

Ongoing credential stuffing attack – how to tackle? from ciso

  1. Credential Stuffing

Credential Stuffing from HackingTechniques