Reusing passwords may feel like a harmless shortcut – until a single breach opens the door to multiple accounts
Reusing the same password across multiple accounts may be convenient, but it sets you up for trouble that can cascade across your digital life. This (bad) habit creates the perfect opening for credential stuffing, a technique where bad actors take a list of previously exposed login credentials and systematically feed the username and password pairs into the login fields of selected online services. And if you recycle the same credentials across various accounts, a single such pair can grant attackers access to otherwise unrelated online services.
Indeed, credential stuffing is the digital equivalent of someone discovering a skeleton key that opens your house, office, and safe – all in one sweep. And finding that key needn’t be difficult at all – it can be gathered from past data breaches and cybercrime markets or attackers can deploy so-called infostealer malware that siphons credentials off compromised devices and web browsers.
What makes credential stuffing so dangerous and effective?
As is probably obvious by now, this threat pays off handsomely for attackers because of our penchant for reusing passwords across accounts – including high-value ones, such as online banking, email, social media and shopping sites. To gauge how common this bad habit is, NordPass recently shared a survey stating that 62% of Americans confess to reusing a password “often” or “always”.
Once an attacker finds login credentials in one place, they can try them everywhere. Then they can use bots or automated tools to “stuff” these credentials into login forms or APIs, sometimes rotating IP addresses and mimicking legitimate user behavior to stay under the radar.
Compared to brute-force attacks, where attackers attempt to guess a password using random or commonly used patterns, credential stuffing is simpler: it relies on what people themselves or their online services of choice have already exposed, often years earlier. Also, unlike brute force attacks, where repeated login failures can trigger alarms, credential stuffing uses credentials that are already valid and the attacks remain under the radar.
While credential stuffing is by no means new, several trends have exacerbated the problem. Info-stealing malware has exploded in volume, quietly capturing credentials directly from web browsers and can even be a threat for password managers. At the same time, attackers can use (AI-assisted) scripts that simulate normal human behavior and slip past basic bot defenses, all while being able to test credential pairs more stealthily and at a greater scale.
Here’s the scale at which credential stuffing attacks can be conducted:
- In 2022, PayPal reported that nearly 35,000 customer accounts were compromised via credential stuffing. The fintech firm itself was not breached – attackers simply leveraged login credentials from older data leaks and accessed accounts belonging to users who had recycled the same passwords across multiple accounts.
- The 2024 attack wave targeting Snowflake customers showed another dimension of the problem. The data storage and processing service itself wasn’t breached, but the incident affected some 165 organizations who were its customers. This was after attackers used credentials previously stolen via infostealer malware to access the firms’ multiple Snowflake accounts, with some victims later receiving ransom demands for stolen data.
How to protect yourself
Here a few practical steps you can take to stay safe. The first step in particular is (disarmingly) simple:
- Never reuse the same password across multiple sites or services. A password manager makes this a breeze as it can generate and store strong, unique passwords for each account.
- Enable two-factor authentication (2FA) wherever possible. Even if attackers know your password, they still won’t be able to log in without that second factor.
- Stay alert and also use services such as haveibeenpwned.com to check whether your email or credentials have been exposed in past leaks or breaches. If they have, take action and change your passwords immediately, especially for accounts storing sensitive data.
How to protect your organization
These days, credential stuffing is also a primary vector for account takeover, fraud, and large-scale data theft across industries, including retail, finance, SaaS, and health care. Many organizations still rely solely on passwords for authentication and even where 2FA is available, it’s by no means always enforced by default. Companies should also restrict login attempts, require network allow-lists or IP whitelisting, monitor for unusual login activity, and adopt bot-detection systems or CAPTCHA to block automated abuse.
Importantly, many organizations are embracing passwordless authentication, such as passkeys, which effectively make credential stuffing useless. Yet adoption remains uneven, and old habits die hard, so it’s little surprise that credential stuffing continues to deliver a high return for attackers with minimal effort.
At the same time, millions of leaked credentials remain valid long after a breach, especially when users never change their passwords. Therefore, credential stuffing is low-cost, highly scalable, and consistently effective for cybercriminals.
Conclusion
Credential stuffing is a surprisingly simple, low-cost and scalable attack technique. It works because its uses our own habits against us and subverts outdated safeguards. Unless you want to move beyond passwords completely, the risk of account break-ins can be neutralized through thoughtful password practices. Those are not optional – they need to be standard practice.
