Credential Stuffing

Credential stuffing bots are automated tools that attempt to gain unauthorised access to user accounts by testing large lists of leaked username-password combinations. These credentials are often obtained from past data breaches and then used across multiple websites, exploiting the fact that many users reuse passwords. Attackers deploy these bots at scale to compromise accounts on banking, e-commerce, and social media platforms, aiming to steal funds, make fraudulent transactions, or take over accounts for further malicious activities.

Impact

Credential stuffing can cause significant financial and reputational damage to businesses and their customers. Customer fraud is a major consequence, leading to unauthorised purchases, stolen loyalty points, or hijacked gift cards. Businesses also suffer from chargebacks and direct financial losses, as fraudulent transactions result in refund claims. Additionally, repeated account breaches erode trust, causing reputational harm that drives customers away. The high volume of automated login attempts can also strain servers, increasing operational costs and degrading website performance.

Example

An e-commerce platform notices a sudden increase in failed login attempts, followed by a spike in customer complaints about unauthorised purchases. Behind the scenes, attackers are using brute-force login bots to test millions of stolen username-password pairs. Once successful, they exploit compromised accounts to redeem gift cards or place fraudulent orders. The company must respond by forcing password resets, handling chargebacks, and implementing additional security measures.

Mitigation

To defend against credential stuffing, businesses employ multi-factor authentication (MFA), login rate limiting, and bot detection solutions. Implementing breach detection services allows companies to identify and block the use of compromised credentials. Additionally, device fingerprinting and behavioural analytics help detect and prevent suspicious login attempts. Encouraging users to adopt unique, strong passwords further reduces the risk of widespread account compromise.