Most dark web monitoring tools work by checking breach databases — collections of stolen credentials that were already published somewhere. That's useful, but it's backwards-looking. Infostealer malware operates in real time, and most monitoring tools don't see it at all.
What infostealer malware does
Infostealer malware is designed specifically to harvest credentials from infected machines. Once installed, it silently reads every saved password from the victim's browser, any password managers that sync to disk, and session cookies that could bypass multi-factor authentication entirely.
That data is packaged and sent to the attacker's infrastructure within minutes. From there it goes to criminal Telegram channels and dark web markets. The most active families — Lumma, RedLine, Vidar, Raccoon — generate thousands of new credential sets every day.
Why standard breach monitoring misses this
A traditional breach database is built from data that was already dumped somewhere public. The data in those databases is often months or years old by the time it's indexed. Infostealer credentials move from infected machine to criminal marketplace in hours and don't always end up in breach databases at all.
What to do if your domain appears
If an employee machine shows up in infostealer data, treat it as a full compromise of that machine. Force password resets across all business services, revoke and reissue any API keys the employee had access to, and investigate whether session tokens were used to bypass MFA.