Credential stuffing: How it hurts your business and how to stop it
Large-scale credential thefts are unfortunately a common occurrence today. But how do fraudsters turn thousands of stolen and compromised credentials into a way to attack your customers’ accounts and gain unauthorized access? This is possible through methods like credential stuffing and by understanding and anticipating these attack types, you can stay one step ahead of fraudsters.
Deploying account security controls that begin to take effect early in the customer journey, far before any money changes hands, can prevent a large percentage of credential attacks or account takeover (ATO) attacks, including those enabled by credential stuffing methods. The key is to add just enough friction to trip up criminals, without slowing down the customer experience to the point of inconvenience and cause friction.
How and why do attackers use credential stuffing to breach customer accounts?
A credential stuffing attack is a specific kind of ATO attempt. Briefly, it involves entering stolen usernames and passwords, often originated from a data breach, into login fields to gain access. This Credential Stuffing is expected to grow based on the following information:
- First, the sheer amount of stolen login credentials leaked each year is enormous. In 2024 alone, there were 3,158 data compromises, with 1.35 billion data breach victims notified about stolen personal information.1
- Secondly, frequent password reuse means breached records may allow attackers to easily break into those individuals’ other accounts — 70% of ATO victims say they didn’t use a unique password for each of their accounts.2
Credential stuffing is part of a family of identity attack types. It is similar to brute force attacks, in which attackers use an automated tool, to populate usernames and passwords and try to gain access into an account. It’s similar to password spraying, which involves entering hacked email addresses and attempting common passwords, although with credential stuffing attacks, the fraudsters know that the email address and password are connected to at least an account, which was part of a data breach.
Despite those similarities, a Credential Stuffing attack is harder to deal with than those related intrusion types because it is more targeted. It sends less obvious warning signs than an attacker using a brute force method to enter thousands of username and password combinations from a single IP address.
Why hackers want access to your customers’ accounts?
What will threat actors do once they’ve executed an ATO attack through methods like credential stuffing? The exact outcome will depend on your industry, and can include:
- Misusing account balances from rewards programs, gift cards, and other currency equivalents.
- Making illegitimate purchases using payment card information associated with the stolen account.
- Engaging in more in-depth identity theft using personal information contained within the breached account.
Stopping attackers before they can reach this point is vitally important for your bottom line and your reputation.
What are the consequences of suffering credential stuffing attacks?
When your customers experience compromised accounts because of a successful credential stuffing attack or similar attack using leaked credentials, the damage can add up quickly. This doesn’t just take one form. It can involve:
- Direct financial consequences: Compensating for the resources stolen from customer accounts and spending money to restore your systems is an immediate form of financial harm. According to IBM, the global average cost of a data breach in 2024 was $4.88M3
- Regulatory penalties: If regulatory bodies in your industry determine that you didn’t do enough to protect customers from account takeover attacks, you may be subject to financial penalties. Compliance is especially important in heavily regulated spaces like healthcare and finance, which deal with highly sensitive information in their everyday operations.
- Reputational damage and loss of trust: This indirect form of harm may end up being the most consequential for your company over the long term. If customers feel they can’t trust your business to protect their personal information, they may engage less and spread negative word of mouth.
Criminals who enter your systems through ATO attacks like Credential Stuffing can leave the compromised accounts unused for long periods of time, striking later and potentially avoiding scrutiny. It’s important to introduce subtle but effective controls and authentication methods throughout the customer journey to stop them, starting at the login screen.
How do you stop Credential Stuffing attacks from affecting your customers?
Credential stuffing attacks have also evolved. Historically, they’ve focused on the login page. Fraudsters have now realized that if they try and create an account with a stolen email address, they often get a warning that the email is already linked with an existing account. When they get that warning, they can now try the login page. If, however, the account can be created, they no longer attempt that email address on the login page, further decreasing the scale of the Credential Stuffing attack on the login page, making it even harder to detect.
When building defenses against Credential Stuffing and similar ATO attack types, it’s important to understand the standard methods of protection, and then go beyond them. Each new tactic from companies receives a counter from threat actors, demanding a response in turn.
For example, standard defenses against Credential Stuffing include locking out users who try to make a huge amount of login attempts with a vast number of email and password combinations. To dodge this tactic, attackers have begun to bombard account creation pages with thousands of stolen email addresses rather than login pages. Only login credentials that elicit a “this address already has an account” response receive further credential stuffing attention.
While basic defenses for preventing Credential Stuffing attacks aren’t useless — they’re worth keeping in place to defend against low-effort, high-volume attacks — your organization should supplement them with more advance, in-depth modern machine-learning methods. These can include:
- Behavioral analysis: How is a user interacting with their account? Are they typing in their username and password or are they pasting or auto-filling. How long do they spend on certain pages? What special character keys, if any, are they using?
- True location detection: Where is a user logging on from? Accounts suddenly being accessed from new locations can receive extra scrutiny.
- Device detection: What type of device is the user accessing their online account from? A sudden change to a computer that has never been associated with a profile is another red flag, as is one device accessing multiple accounts.
- Suspicious login attempt analysis: Is a person using techniques associated with either automated or human criminal behavior? This could mean over familiarity of an account create screen, navigating quickly between fields. Or it could mean not filling out fields in a systematic way, but the way the bot has been created or a human criminal following data from a spreadsheet. It could also involve signals of automated activity by bots, such as a cursor that never moves.
These methods are at their best and most effective when they run in the background as part of an automated threat prevention system, undetectable to legitimate users for a friction-free customer experience.
Combine tech with humanity for extra online account protection
At Accertify, our solutions are designed to provide support against the ever-evolving ATO tactics favored by today’s attackers, including Credential Stuffing. Our platforms combine advanced machine learning technology with human insights designed to help keeping businesses one step ahead of the latest attack types.
Accertify’s offerings provide end-to-end bespoke protection for each step of your digital customer journey — at account creation, login, pre-payment, checkout, and all through the life span of a customer account. This is the level of protection needed to defend your bottom line and your reputation.
Learn more about how Accertify’s account protection solutions can prevent the damage that comes from a compromised account.
[1] ITRC, 2025
[3] https://www.idtheftcenter.org/publication/2024-data-breach-report/