Why credential stuffing starts with stealer logs
Most credential stuffing attacks don't start with a breach dump — they start with an infostealer log. Here's the actual supply chain, and where defenders can interrupt it.
What a stealer log actually contains
An infostealer infection doesn't just harvest a password. It exports the browser's entire saved-credential store — username, password, and the exact URL the pair was saved against — plus session cookies, autofill data, and often a system fingerprint. That combination is what makes stealer logs more dangerous than a plain breach dump: a breach gives an attacker a password, a stealer log gives them a working login for a specific site, often still valid.
From infection to stuffing list
The path from infection to attack has a predictable shape. A stealer infects a machine, usually through a cracked-software installer, a fake update, or a malicious ad. The malware phones home to a panel, the operator packages the harvested data into a log, and that log is sold or traded on stealer marketplaces and Telegram channels — frequently within hours of infection. From there, a second group of actors — not the original operator — extracts every username/password pair tied to a target's domains and feeds them into credential-stuffing tooling that tries each pair against the target's live login pages.
Where defenders can actually interrupt it
The window between a log appearing on a marketplace and its credentials being stuffed against your login page is the only point a defender fully controls. Waiting for a stuffing attempt to show up in login telemetry means reacting after the fact. Continuously matching new stealer-log records against your own domains — before they're weaponized — turns credential exposure into a routine password reset instead of an incident.
Frequently asked questions
- Is a stealer log the same thing as a data breach?
- No. A data breach exposes data a company held about its users. A stealer log is harvested directly from an infected individual's device — browser-saved passwords, session cookies, and autofill data — regardless of whether any company was breached at all.
- Why are stealer-log credentials more dangerous than breach-dump credentials?
- A stealer log ties a password to the exact URL it was saved against and is often only weeks or days old, so the credential is far more likely to still be valid than one pulled from an old breach dump.
- Can credential stuffing be stopped with rate limiting alone?
- Rate limiting slows automated stuffing attempts but does nothing about the underlying exposed credential — the same password still works once an attacker paces requests below the limit. Rotating the exposed credential before it's used removes the attack entirely.
Test your own domain
StealerHunt continuously scans stealer logs and leak archives, matching every record against your domains. Check for free whether your organization has exposed credentials.