What is Credential Stuffing and How to Prevent It

In this day and age, cyberattacks are no secret, and the rate of them seems to keep rising. These kinds of attacks seem to take place every second, and in this case, it’s credential stuffing.

It’s not a dramatic kind of hack with codes splattering across your screen; it’s a quieter, more insidious threat that leverages our own bad habits against us. It’s called credential stuffing, and if you use the same password for more than one website, you are at a higher risk. 

This isn’t about a company you trust getting breached; it’s about what happens after the breach, when your login details are sold on the dark web and tested on thousands of other digital accounts.

What is Credential Stuffing?

Credential stuffing is a type of cyberattack in which hackers take vast lists of stolen usernames and passwords from one data breach and systematically try them on countless other websites and services.

To think of it in clearer light, picture a bunch of criminals stealing a massive batch of keys labeled “Home.” Instead of trying to figure out which key belongs to which house, they simply walk down a street and try every single key in every single front door. Eventually, they find a lock that one of the keys opens. Credential stuffing works on the same principle, but at a scale of millions of attempts per hour.

The entire attack depends on the most common human behavior: password reuse. Most people use the same email and password combination for their social media, their online banking apps, online shopping, streaming services, and others. Attackers know this and roll out every possible method or process of exploiting it.

How Does Credential Stuffing Work?

The process that hackers use is methodical, and they often utilize some of the most sophisticated automation tools. Here is a breakdown of how credential stuffing works: 

Acquisition

Attackers begin by acquiring a “combo list”, which is a huge collection of login credentials stolen from previous company data breaches. These lists, which pair usernames (often email addresses) with passwords, are easily purchased on the dark web. They represent a compiled history of digital break-ins, aggregated from thousands of sources.

Automation

Next, we have automation, a step where the attacker uses specialized software called a “bot” or “credential stuffing tool.” You will not find the hacker manually typing in passwords; they use software that makes thousands of login attempts per minute from different IP addresses. They use different IP addresses to avoid detection.

The Attack Cycle

After the automation process, the bot is fed the combo list and pointed at a target website’s login page (e.g., a banking site, a streaming service). It then runs a relentless cycle where the bot systematically tests each stolen login pair. It then feeds the credentials into the website and analyzes the feedback. If there are any failed attempts, it is ignored, but any successful login is flagged as a valuable “hit.” The bot then securely notes this verified account information and proceeds to test the next combination on its list.

Monetization

Now that all three steps are complete and the hacker has access to a large number of accounts and codes, the real damage begins. What they do is plunder all the accounts directly, steal saved credit card information, personal data, loyalty points, etc., whichever is most valuable. They also sell all these validated accounts to the criminals on the dark web, ofcouse who are the highest bidders. They further use these accessed accounts to launch other attacks, for example, to scam the user’s contact list. That is one of the biggest ways hackers monetize credential stuffing attacks.

Credential Stuffing and Brute Force Attacks Comparison

Even though credential stuffing is not the same as a brute force attack, it is still considered a kind of brute force attack. Yes, both aim to gain unauthorized access, but credential stuffing and brute-force attacks differ fundamentally in their approaches and efficiency. Take a look below at the core differences between credential stuffing vs brute force attacks: 

What is the Impact of Credential Stuffing?

When a credential stuffing attack succeeds, it creates a strong ripple effect that can severely affect both individuals and businesses.

The Issues It Causes for Individuals

Here are a few circumstances that show the impact of credential stuffing on individuals: 

Financial loss

Through this attack, hackers can completely drain out bank accounts. They can do this by making unauthorized purchases using your stored payment methods or redeeming gift cards and loyalty points.

Identity theft

If the attacker gets access to an email or social media account via an instigated credential stuffing attack, they can gather enough personal information to commit full-scale identity theft.

Account takeover

You can lose access to your own email IDs, social media accounts, or gaming accounts, which may be used to scam your friends and followers.

Data loss

The impact of this attack can result in your personal photos, messages, and documents stored in cloud services being stolen or deleted.

Reputational damage

A compromised social account can be used to post harmful content, damaging your personal and professional reputation.

For Businesses

Here are a few circumstances that show the impact of credential stuffing on businesses: 

Direct financial fraud

Businesses that are attacked will have to bear the cost of fraudulent transactions and chargebacks.

Reputational damage and erosion of trust

If businesses that handle large user accounts are attacked, their customers lose faith in the company. They assume that they cannot protect their accounts.

Legal and compliance penalties

Potential fines for failing to protect user data under regulations like GDPR or CCPA.

Customer churn

Frustrated users who feel unsafe will take their business elsewhere.

Increased support costs

A flood of support tickets from locked-out and compromised users strains customer service resources.

Degraded performance

The massive bot traffic from an attack can slow down or even crash websites, affecting all users.

How to Detect Credential Stuffing

Before moving on to ways you can prevent credential attacks, here are a few ways to detect them: 

A Sudden, Massive Spike in Login Attempts

Your website traffic data will reveal a sudden, massive spike in visits to the login page, a volume that is impossible for real human users to generate.

A High Rate of Login Failures

Even though the attackers have real passwords, they are trying them against the wrong accounts, leading to a large volume of failed logins. However, the failure rate will be lower than in a brute force attack because some attempts will succeed.

Traffic from Unusual Geographies

You will see a spike in login attempts that are located in countries or locations where the business does not even have customers. This is a straight detection of an attempted credential or online account attack. 

Traffic from Known Botnets

To conceal their true location, hackers channel their attacks through intermediary services like proxies and Tor exit nodes.

Multiple Login Attempts via a Single Account

While the attack uses many credentials, bots will also retry usernames with different passwords, triggering account lockout policies.

How to Prevent Credential Stuffing Attacks

Protection requires a multi-layered defense strategy that combines technology with user education. Here are a few ways showing you how to prevent further attacks: 

1. Use a password manager: This is the single most effective step you can take. A password manager helps generate and store strong, unique passwords to protect the sites and apps you use. You only need to remember one master password. With FastestPass, you get all these perks and more. 
2. Enable multi-factor authentication: This is important for both individuals and businesses. MFA adds a significant step to login processes, such as entering a code sent to your phone. Even if a hacker has your correct password, they cannot log in without this second factor.
3. Deploy advanced bot detection: Use services that can distinguish between human users and malicious bots based on behavior, such as mouse movements, keystroke dynamics, and IP reputation. This is especially important for business owners.
4. Use unique passwords: If you don’t use a password manager, make a concerted effort to use different passwords for different services, especially for your email and financial accounts.
5. Monitor for credential spills: Proactively search the dark web for lists of your users’ credentials. If you find them, you can force a password reset for the affected accounts before they are used in an attack. This might sound a little tasking, but it’s crucial if you want your business to thrive and remain safe.
6. Monitor your online accounts: Regularly check your bank and credit card statements for suspicious activity. Use services like: Have I Been Pwned? to see if your email has been involved in a known data breach.
7. Rate limiting: To prevent these attacks in the future, you need to add rules that limit the number of login attempts from a single IP address or for a single username within a specific time frame.

Frequently Asked Questions

To Conclude

Credential stuffing is a pervasive threat, but that doesn’t mean it can’t be prevented or detected.  If you simply try to understand how it works, going through ways to control it, you can take the effective steps, both as an individual and as a business, to create way more safety in today’s digital space. The best ways to prevent this kind of credential attack are to incorporate both security tools and increased knowledge of the best practices, eliminating repeated human mistakes.