What is infostealer malware?
Infostealer malware harvests authentication and identity data from an infected device and exfiltrates it to attacker infrastructure. A single device’s complete package is a stealer log. Infostealers are the dominant supplier of fresh, plaintext credentials and live session cookies in the underground today.
What makes infostealers so dangerous
Two traits define the threat:
- Breadth. One infection captures credentials across every browser, active session cookies and tokens, autofill, device fingerprints, and wallets – everything needed to impersonate the victim across all their accounts.
- Forensic evasion. Many variants execute, harvest, and self-delete in seconds, leaving no files, registry keys, or behavioral indicators. EDR and antivirus may never flag it.
The first evidence often appears not in your logs but in criminal markets, when the stolen data goes up for sale.
How do I check if my company has devices infected by infostealers?
Run Check Your Exposure to see whether devices tied to your domain have been infected by infostealer malware and are leaking identity data. Infostealers siphon credentials and session cookies straight from the device and often run without being caught by endpoint defenses, so this can surface exposure your tools missed.
The enterprise blind spot and why a password reset isn't enough
Corporate controls protect managed devices; infostealers target the ones you don’t manage, and the standard response leaves the attacker in:
- Unmanaged devices. Infections land on home and personal machines that still hold corporate credentials, VPN tokens, and Microsoft 365 sessions – with no IT visibility.
- Live sessions survive a reset. Logs carry session cookies valid until the app kills them; the buyer keeps access after a password change.
- Remediate the full scope. Complete post-infection remediation invalidates every active session on top of resetting credentials.
- Get the inventory. SpyCloud Endpoint Threat Protection surfaces the per-device exfiltration list so you remediate exactly what was taken.
Notable infostealer families
Infostealer malware is sold and run as a service, with a handful of families dominating the market at any given time. Recent and recurring names include:
- LummaC2 (Lumma) – among the most prevalent malware-as-a-service stealers, targeting browser credentials, cookies, and crypto wallets.
- Vidar and StealC – long-running families repeatedly repackaged and redistributed across criminal markets.
- RedLine and Raccoon – historically high-volume stealers whose logs keep circulating and feeding combolists long after a campaign ends.
Families rise and fall as operators are disrupted, but the model is constant: low-cost subscriptions producing fresh, plaintext credentials and live session cookies at scale.
Infostealers run quietly and steal everything at once.
See which identities tied to your domain they have already exposed.
Frequently Asked
All available authentication data from a device: browser credentials across all browsers, active session cookies and tokens (enabling MFA bypass), autofill data, device and browser fingerprints, crypto wallets, and email or messaging data. The complete package is a stealer log. SpyCloud documented 18.1 million exposed API keys and tokens from malware sources alone in its 2026 report.
Many variants are non-persistent – they run, harvest, and self-delete in seconds, leaving no artifacts for endpoint tools. The first sign of compromise usually surfaces in criminal markets when the stolen data is listed, which is why darknet monitoring is a detection layer independent of endpoint security.
No. Logs contain active session cookies that stay valid until the application invalidates them, regardless of the password. An attacker can keep using the hijacked session after a reset. Complete remediation requires invalidating all active sessions across affected applications in addition to credential resets.