Definition
Credential stuffing is a type of cyberattack where attackers use large lists of stolen usernames and passwords, often obtained from data breaches, to gain unauthorized access to user accounts. Attackers automate the process by using bots to systematically try these credentials across various websites and online services. This attack method exploits the common practice of users reusing the same login information across multiple platforms, making it a significant threat to online security. For instance, if a popular social media site experiences a data breach, attackers will immediately try those compromised credentials on banking sites or email providers. Unlike brute force attacks that guess passwords, credential stuffing uses pre-existing, valid login pairs. This technique is frequently covered in cybersecurity certifications like CompTIA Security+ and CySA+ as it represents a pervasive real-world threat.