Overview
Stealer logs are one of the most dangerous — and least understood — sources of credential exposure. Unlike traditional data breaches where a company's database is hacked, stealer logs come from malware installed on individual computers that silently harvest every saved password, cookie, and browser session.
What Is Info-Stealer Malware?
Info-stealer malware is a category of malicious software designed to extract sensitive data from infected computers. The most common info-stealers include:
- RedLine Stealer — the most prevalent info-stealer, often distributed through fake game cheats, cracked software, and phishing emails
- Raccoon Stealer — sold as a Malware-as-a-Service (MaaS) subscription on dark web forums
- Vidar Stealer — targets browsers, crypto wallets, and 2FA applications
- Lumma Stealer — newer stealer focusing on browser-stored credentials and extension data
How the Infection Chain Works
- Distribution: The malware is spread through phishing emails, fake software downloads, malicious ads, or compromised websites
- Execution: Once a user runs the malicious file, the stealer activates silently — often running for just a few seconds
- Harvesting: The malware extracts:
- All saved passwords from Chrome, Firefox, Edge, and other browsers
- Active session cookies (can bypass MFA)
- Autofill data (credit cards, addresses)
- Browser history and bookmarks
- Cryptocurrency wallet files
- Application data (Discord, Telegram, VPN clients)
- Exfiltration: The harvested data is compressed and sent to the attacker's server
- Sale: The data is packaged and sold on dark web marketplaces, Telegram channels, or dedicated log shops
The ULP Format
Stealer logs are typically organized in URL:Login:Password (ULP) format:
https://mail.company.com:[email protected]:P@ssw0rd123
https://vpn.company.com:[email protected]:P@ssw0rd123
https://slack.com:[email protected]:P@ssw0rd123
A single infected employee's computer can yield dozens to hundreds of corporate credential pairs — for email, VPN, SaaS applications, internal tools, and more.
Why Stealer Logs Are Worse Than Traditional Breaches
| Factor | Traditional Breach | Stealer Logs |
|---|---|---|
| Source | Company's server is hacked | Individual device is infected |
| Scope | Limited to that company's database | Captures ALL saved passwords across ALL services |
| Freshness | Data may be months/years old | Data is typically hours/days old |
| MFA bypass | Generally can't bypass MFA | Session cookies can bypass MFA |
| Detection | Company may notify affected users | User often has no idea they're infected |
| Volume | 500M+ new credentials appear daily | Growing exponentially |
Why Corporate Credentials End Up in Stealer Logs
An employee doesn't need to be targeted directly. Common scenarios include:
- A employee's personal laptop is infected after downloading cracked software — but they also use that laptop to check work email
- An employee's child or family member installs a game cheat on a shared computer that has corporate bookmarks
- An employee clicks a phishing link that installs a stealer instead of (or in addition to) a phishing page
- A contractor or freelancer working from an unmanaged device gets infected
The key insight: corporate credentials are exposed not because your company was breached, but because an individual's device was compromised.
How Verusight Helps
Verusight monitors for your domain's credentials appearing in stealer log collections and breach databases. When credentials are found:
- You're alerted immediately (Pro Guard)
- You can see which employees are affected and which services are compromised
- You can take action before attackers use the stolen credentials
Recommended Protective Measures
- Deploy credential monitoring — know when your employees' passwords appear in stealer logs
- Enforce MFA on all corporate services — while stealer session cookies can bypass MFA, it still adds a critical layer
- Implement endpoint detection (EDR/XDR) — detect and block info-stealer malware before it can harvest credentials
- Restrict personal device usage for corporate accounts when possible
- Educate employees about the risks of saving corporate passwords in personal browsers and downloading unverified software