Stop Credential Stuffing with Prosopo

What is Credential Stuffing?

Credential stuffing is a type of cyberattack in which automated bots attempt to log in to user accounts using stolen username and password combinations. These credentials are often obtained from previous data breaches and sold or shared on the dark web. Because many users reuse passwords across multiple platforms, even a breach on a single site can put accounts on other services at risk.

These attacks are highly automated, leveraging large lists of credentials and testing them against multiple websites in rapid succession. This makes them extremely efficient and difficult to detect without specialized security measures. According to Have I Been Pwned, credential breaches are widespread, highlighting the importance of proactive protection.

Why Credential Stuffing is Dangerous

Credential stuffing is particularly threatening because it exploits common user habits rather than technical vulnerabilities:

• Password Reuse: Even platforms that have never been breached are vulnerable if users recycle passwords from other sites.
• Financial Loss: Attackers can use access to perform fraudulent transactions, transfer funds, or make purchases.
• Data Theft: Sensitive information such as email addresses, personal details, and business data can be extracted.
• Trust Erosion: Users lose confidence in platforms that fail to protect their accounts, potentially harming brand reputation.
• Stealthy Attacks: Bots often operate in ways that mimic normal user behavior, making detection more challenging.

Credential stuffing attacks can occur silently, often going unnoticed until significant damage has been done.

How Prosopo Protects Against Credential Stuffing

Prosopo sits on every login endpoint and scores each request as it arrives. Credential-stuffing infrastructure looks different from legitimate sign-ins across several signals, and Prosopo reads them all:

• Network-wide behavioural modelling. Mouse cadence, scroll patterns, typing rhythm and device fingerprints are continuously modelled across our platform — credentials-replay tools that pass on one site fail on the next.
• Residential proxy and real-device farm detection. Stuffing operators route through residential IPs and real-device farms to evade IP reputation lists. Prosopo's risk scoring labels those networks even when the IP itself has a clean record.
• Surge detection on login endpoints. A normal login page sees steady, geographically-distributed traffic. A sudden spike from hosting ASNs or out-of-country networks triggers automatic step-up verification on that traffic — without touching legitimate sign-ins.
• Advanced ML adapting in real time. Our machine-learning models retrain continuously against new stuffing toolkits and bypass patterns, so countermeasures emerge during the attack rather than after the fact.
• Invisible for real users and trusted agents. Legitimate logins (including password-manager and AI-agent sessions) pass with zero friction; suspicious sessions get a proof-of-work or image challenge; known-bad traffic is blocked at the door.

The result: real users sign in unimpeded, agents acting on a user's behalf are recognised, and credential-stuffing infrastructure stops dead at the login form.

Recommended products

• Risk Scoring — flag high-risk login attempts so your backend can require step-up authentication on borderline scores.
• Access Control — block hosting networks, abusive ASNs and TLS fingerprints associated with breached-credential replay.
• Invisible CAPTCHA — stop automation at login without adding visible friction for legitimate users.