Credential Stuffing Bot

Credential stuffing exploits the fact that people reuse passwords across sites. Attackers obtain combolists of usernames and passwords leaked from unrelated breaches, then use a bot to submit each pair to a target's login form. Every successful login is an account the attacker can now control, monetize, or resell.

To succeed at volume, the bot must evade rate limiting and detection. It distributes attempts across many IP addresses using proxy pools, paces requests to avoid tripping thresholds, and often drives headless browsers so it can execute the JavaScript and challenges a modern login page presents. When challenges appear, the operation may route them to a CAPTCHA farm.

The economics are lopsided in the attacker's favor. Even a low success rate is profitable because the input credentials are cheap and the process is fully automated, so millions of attempts can yield a worthwhile number of valid logins. This is why raw attempt volume, not cleverness per attempt, defines the threat.

Defenses aim to break the volume rather than judge each attempt in isolation. Velocity checks catch bursts against many accounts, network intelligence flags suspect origins, and device identification links attempts that rotate their surface disguises. Recognizing the automation itself is what prevents the bot from simply spreading its attempts thin enough to slip past per-account limits.