Account takeovers are a nightmare scenario for anyone. Having somebody else gain access to your finances or most sensitive data is extremely stressful and can impact your whole life. Imagine somebody emptying your bank account or taking out credit cards in your name.
There is an onus on people to ensure that they are protected and don’t fall foul of credential stuffing attacks. Setting up strong, unique passwords and monitoring your data closely are essential for protecting yourself from attacks.
What is credential stuffing?
Credential stuffing is where criminals use stolen usernames and passwords (often gathered from previous data breaches to try and break into online accounts. Because many people reuse passwords across different platforms, one login often grants access to multiple accounts. That’s exactly what hackers count on for their targeting.
The cybercriminals use automated tools or “bots” to fire thousands of login attempts at a time, hitting as many sites as possible.
These bots are fast and programmed to mimic real human behaviour, making them harder to spot and block. Just one cracked account can lead to stolen money and identity theft.
How credential stuffing attacks work
The process of credential stuffing means acquiring stolen data and using this to try and access accounts on banks as well as other secure sites. Hackers find (or buy) personal data and then automate the process of login attempts to try and log into accounts.
Data collection
Everything starts with stolen data. Hackers don’t always need to break into a site to get passwords as there are plenty already floating around the internet. Many stolen credentials end up on the dark web – a hidden part of the internet where cybercriminals can buy and sell hacked data.
These login credentials often come from previous data breaches and are freely traded or sold in large batches.
Some collections, like the infamous “Collection #1-5,” contain billions of usernames and passwords. It’s a goldmine for cybercriminals, and all it takes is one match on another platform.
Automated login attempts
Once the hackers have their stash of stolen credentials, the next step is testing them. That’s where automation comes in.
Attackers launch large-scale login attempts across multiple websites, checking if any of the stolen combinations still work. These bots are smart and some use headless browsers (a web browser that runs without a graphical user interface, in the background and is controlled programmatically—typically for automated tasks) or rotate IP addresses in an attempt to avoid detection. They even add delays between login attempts to trick systems into thinking it’s a normal user logging in, avoiding suspicion or security protocols.
Account takeover
When credentials match and a login is successful, hackers gain full control of the account, for example the email account.
From there, they can attempt to drain bank accounts, steal private data, or even lock the real owner out. Hackers have different approaches depending on which accounts they can take over. If they don’t get into your bank and empty it, they can still use the email account access for other crimes like sending phishing messages to other accounts to hack them too. They may also sell compromised accounts to other criminals. In short, a single successful login can spiral into a mess for the user.
Credential stuffing vs. brute force vs. password spraying
These three attack types all target passwords, but the methods differ.
Credential stuffing
Credential stuffing relies on real, previously stolen passwords. Hackers aren’t guessing, they’re using existing data. The attack’s success depends on how many people have reused their passwords across platforms.
Brute force attacks
Brute force are more of a guessing game. The attacker tries random password combinations over and over again until one eventually works. It’s automated but is a slower method and easier to spot since it usually involves lots of failed attempts from the same IP address.
Password spraying
Password spraying is a mix between brute force and credential stuffing. Hackers try common passwords—like “password123” or “123456” on a large number of accounts such as those they have found on Collection #1. This method is sneaky because it avoids detection systems that flag repeated failed attempts on a single account.
Why credential stuffing is a growing threat
Credential stuffing is getting worse. One reason is the huge amount of stolen credentials available online. Collections like the ones mentioned earlier give attackers an endless supply of potential logins to test and feed their systems. As long as people keep reusing passwords, the risk remains high.
Another problem is the technology behind these attacks. Bots are getting more advanced.
Tools like headless browsers let them behave just like real users, and IP spoofing helps them dodge detection systems. By integrating plugins and customizing the browsers, attackers can fine-tune them to try to mimic user behavior. Some bots can even solve CAPTCHA challenges or imitate mouse movements. To counter this, websites can use device fingerprinting, which tracks a user’s browser, device type, and behavior patterns to detect suspicious logins and block automated attacks.
On top of that, the number of online accounts has exploded. Most of us have dozens of logins. That means more targets for attackers to try their luck on and more potential places for credentials to be stolen.
Password habits haven’t kept up with the threats. Many people still use simple and guessable passwords or the same one across multiple sites. 84% of users, according to one study, are using risky passwords for online accounts. All it takes is one breach, and suddenly a hacker has access to everything from emails to financial accounts.
Real-world examples of credential stuffing attacks
Credential stuffing isn’t just a theoretical threat. It’s already caused chaos for some major names across different industries.
One high-profile example involved HSBC Bank, where attackers used stolen logins to access customer accounts. This breach allowed unauthorized access to financial data and the company even had to suspend its entire online login process while things were sorted. As many as 14,000 customers were impacted.
Over on Reddit, users found themselves suddenly locked out of their accounts after a wave of credential stuffing attacks hit the platform. Reddit had to ask users to reset their passwords if they were able to access their accounts.
Another significant case came from TurboTax, where attackers used stolen credentials to access tax information in a 2019 attack. This wasn’t just about usernames and passwords as once inside, criminals could access Social Security Numbers and other sensitive personal data.
Nintendo also experienced a massive breach where thousands of Nintendo Network ID accounts were compromised. Attackers managed to break into accounts using reused credentials, leading to unauthorized purchases and privacy concerns for gamers. A massive 300,000 accounts were compromised.
The impact of credential stuffing
Credential stuffing attacks can lead to some huge issues. It’s possible that victims will get locked out of accounts, and that money will be stolen directly, or through other fraudulent methods like applying for credit cards using their details.
Financial loss
One of the most immediate and visible consequences of a credential stuffing attack is the financial damage it can cause. Once an attacker gains access to a payment or bank account, it doesn’t take long for funds to start disappearing.
Victims often face weeks of back-and-forth with their banks or card providers just to sort out the mess and try to get the money back. This can cause immense stress.
Identity theft
Beyond the money, credential stuffing opens the door to something even more dangerous; identity theft.
If attackers can get their hands on enough personal details, they can pose as someone else. They might apply for new accounts or even commit fraud and other crimes using someone else’s name. The damage from identity theft can follow a person for years and often takes a long time to fully untangle.
Privacy invasion
There’s also the issue of personal space. When attackers break into an account, they don’t just see numbers and passwords, they gain access to private details. Things like private pictures and personal data can be leaked. That’s a serious invasion of privacy. The idea that someone can browse through conversations or files without permission is disturbing and unsettling for anyone involved.
How users can protect themselves from credential stuffing
Users need strong protections from credential stuffing including healthy passwords and other methods like two-factor authentication or multi-factor authentication.
Using a VPN (Virtual Private Network) can add an extra layer of security by masking your IP address, making it harder for hackers to track your online activity or target you with credential stuffing attacks. Using unique passwords for every site or service may sound like a hassle, but password managers make it easy.
2FA is also possible with lots of online accounts. Use it wherever you can. Even if someone manages to steal a password, 2FA puts an extra wall in the way. It usually means entering a code sent to a phone or email which makes it harder for attackers to break in unnoticed (unless they are already in your email account).
It also helps to stay informed. Digital footprint scanner offers Dark Web monitoring and more to allow you to check if their email or credentials have been exposed in any known data breaches. It’s a useful way to stay ahead of threats and know when it’s time to update passwords, and it is easy to search your email address and see where it appears in leaks.
Related articles:
Your Social Security Number is already exposed – now what?