What Are Stealer Logs?
Stealer logs are the structured archives of data that infostealer malware exfiltrates from an infected device: saved browser passwords, session cookies, autofill entries, cryptocurrency wallet files, and a fingerprint of the machine itself. A data breach pulls records from a company's central database; a stealer log comes from a single end user's device and carries live session tokens that breach data lacks.
Operators package the stolen data into archives and sell them in underground marketplaces (opens in new tab), where other criminals buy them for follow-on attacks.
How stealer logs work
An infostealer reaches a device through a lure, runs once, harvests everything it can reach, and exits. Phishing attacks remain the main distribution vector (opens in new tab), and LummaC2 payloads arrive through spearphishing links (opens in new tab) and attachments. The ClickFix technique (opens in new tab) shows a fake error or CAPTCHA prompt that tells the user to paste a command into the Windows Run dialog, and the pasted script downloads the payload.
Attackers also use SEO poisoning download pages and promote cracked software through video and messaging platforms as common entry points.
Once running, the malware decrypts the browser credential stores that Chromium and Firefox treat as protected. This behavior is browser credential access (opens in new tab). In July 2024, Google shipped Chrome's App-Bound Encryption (opens in new tab), which moved cookie decryption behind a SYSTEM-level service. Attackers responded with remote-debugging techniques (opens in new tab) that extract cookies through Chrome itself.
The malware places each data class in its own file, compresses the folder, and sends the archive (opens in new tab) to command-and-control infrastructure or shares it through services such as Telegram.
The operation runs as malware-as-a-service: developers rent builders and web panels (opens in new tab), distributors handle infection campaigns, and markets such as Russian Market and 2easy sell the logs on (opens in new tab) to the next buyer.
Why stealer logs are hard to stop
A valid session cookie can let an attacker bypass a fresh login. Session cookies stay valid for an extended period even when the application is not in use, and they can bypass some MFA protocols (opens in new tab). The attacker loads the cookie into an anti-detect browser and resumes a session the victim already authenticated; depending on the application, a password reset can leave that session open because active session tokens (opens in new tab) require separate revocation.
The infection itself leaves little trace: an infostealer collects what it can and exits, so the business often can't connect it to what comes later. On personal and contractor devices (opens in new tab) with no EDR, an external marketplace listing can be the first signal.
A single working corporate account is extremely valuable to buyers (opens in new tab) because it can unlock many enterprise systems at once, especially where a stolen cookie sidesteps MFA.
Credentials outlive the malware that stole them. Microsoft and the DOJ disrupted Lumma's infrastructure in May 2025 in an action coordinated with Europol (opens in new tab), and Vidar displaced Lumma (opens in new tab) as the most-used infostealer on Russian Market.
Operation Endgame hit StealC and Amadey (opens in new tab) in June 2026, and seizures can move supply between families while the logs criminals already sold keep working.
What a stealer log contains
Each archive holds a set of top-level files and folders per infected endpoint:
- Passwords.txt: Saved browser logins as URL, username, and password triples, which the malware decrypts from Chromium and Firefox credential stores.
- Cookies: One file per browser profile holding the session cookies (opens in new tab) that allow replay without a password.
- Autofill.txt: Names, addresses, and saved credit card data the browser stored for form completion.
- Wallets: Desktop wallets and browser extensions containing cryptocurrency wallet data.
- System.txt and Screen.png: Windows version, hostname, hardware ID, external IP, running processes, antivirus products, and geolocation, plus a screenshot the malware takes at infection time.
- Application sessions: Telegram data, Discord tokens, VPN credentials, and FTP logins collected from installed applications.
- Files: Documents the malware collects from the device, some exposing passwords or wallet recovery phrases.
How to defend against stealer logs
Effective defense spans authentication, monitoring, and response:
- Deploy phishing-resistant authentication. FIDO/WebAuthn (opens in new tab) protects the login event, but infostealers can still steal the session token issued afterward, so pair it with controls that restrict session replay and require trusted devices.
- Require compliant devices. Requiring compliant devices (opens in new tab) blocks access from unmanaged personal laptops; BYOD alone creates security limits (opens in new tab) no configuration fully closes.
- Monitor for exposure. Continuous monitoring of criminal marketplaces, Telegram log channels, and forums for the corporate domain gives early warning when credentials surface, covering public breach datasets and logs where employees entered the company's own credentials.
- Watch the endpoint. Behavioral detection for unexpected browser credential-file access (opens in new tab) and suspicious PowerShell execution (opens in new tab) catches ClickFix chains in progress.
- Revoke before you reset. Revoke refresh tokens (opens in new tab), disable the compromised device, invalidate active access tokens, and reset affected passwords from a trusted device.
Audit VPN, HR, and finance tools that sit outside centralized identity management, and review new device and MFA registrations in the hours after the estimated infection time.
How Doppel helps
Doppel is the Frontier AI Social Engineering Defense (SED) platform unifying Digital Risk Protection (DRP) and Human Risk Management (HRM). Executive Protection detects exposed employee and executive credentials across dark web marketplaces and Telegram log channels.
Doppel's agentic AI correlates, prioritizes, and dismantles impersonation infrastructure through platform APIs and escalation paths, while analysts handle escalations requiring human judgment. Teams can convert a live ClickFix campaign into an employee Simulation in one click, turning the observed lure into the next training exercise.
Request a demo to see how the platform detects credential exposure, maps related campaigns, dismantles impersonation infrastructure, and converts live lures into simulations.
Frequently asked questions about stealer logs
What are stealer logs?
Stealer logs are archives of stolen data that infostealer malware produces while running on an infected computer. A typical log contains saved browser passwords, session cookies, autofill and payment data, cryptocurrency wallet files, application tokens for services like Telegram and Discord, and a system profile including the machine's IP address and installed software. Malware families such as LummaC2, Vidar, StealC, RedLine, and Atomic Stealer on macOS send these logs to the operator over a command-and-control panel or a Telegram bot.
What are stealer logs in cybersecurity?
In security operations, stealer logs are a major supply of working credentials and live sessions that criminals trade. Initial access brokers search logs for VPN, remote desktop, and single sign-on credentials, validate them, and resell the access to ransomware operators, making credential-based access a top initial-access vector. Security teams treat a corporate credential found in a log as an active incident and run a full incident response alongside malware cleanup on the affected machine.
Stealer logs vs. combolists: what is the difference?
A stealer log is the raw output of one infection: credentials, cookies, files, and system data taken from a single device, often soon after the theft. A combolist is a bulk file of username and password pairs that criminals compile from many sources, including old stealer logs, database leaks, earlier combolists, and sometimes autogenerated data, and format for credential stuffing attacks. The log is the more dangerous of the two because fresh session cookies allow immediate account takeover without a password or a second authentication factor. The same credential in a combolist forces the attacker to guess which services still accept it.
What is an example of a stealer log attack?
A stealer log attack can begin when malware infects an employee or contractor device and captures credentials for a corporate file-sharing, cloud, or identity platform. A buyer can then validate those credentials or replay an active session to access enterprise data without compromising the company's servers directly. If the organization resets only the password but does not revoke active sessions, the stolen session can remain usable. The scenario shows why security teams monitor criminal markets for their own domain, revoke sessions, and reset passwords when exposure appears.