Infostealer 101
What is infostealer malware?
Infostealer malware silently harvests passwords, browser data, and sensitive information from infected devices - then sends it straight to cybercriminals.
How Infostealers Collect Data
Modern infostealers are sophisticated tools designed to extract maximum value from infected machines in seconds.
Passwords.txtSaved Passwords
Extracts stored credentials from Chrome, Firefox, Edge, and other browsers - including passwords you thought were secure.
Autofill/Autofill Data
Harvests addresses, phone numbers, and payment card details stored in browser autofill features.
Wallets/Cryptocurrency Wallets
Targets wallet files and browser extensions for Bitcoin, Ethereum, and other cryptocurrencies.
Applications/Application Data
Extracts credentials from VPN clients, email applications, FTP software, and other business tools.
System.txtSystem Information
Collects hardware IDs, installed software, and network details to profile victims and bypass security measures.
How Data Reaches Criminals
From infection to sale, stolen credentials move through a well-organised supply chain.
Infection
Victim downloads malicious software - often disguised as cracked software, game cheats, or legitimate-looking email attachments.
Harvesting
The malware executes silently, extracting saved passwords and browser data in seconds. Some variants include keyloggers that capture new passwords as they're typed - sending them to attackers within milliseconds.
Exfiltration
Stolen data is encrypted and sent to attacker-controlled servers via Telegram, Discord, or private servers.
Packaging
Data is compiled into structured 'logs' - organised folders containing all stolen information from each victim.
Distribution
Logs are sold in bulk on dark web marketplaces, Telegram channels, and automated credential shops.
How Does This Affect Your Business?
Stolen credentials create real costs - from lost revenue to expensive breach response.
Account Fraud & Chargebacks
When criminals use stolen credentials to access customer accounts, they make fraudulent purchases, drain loyalty points, or steal stored payment methods. You're left handling chargebacks, refunds, and angry customers.
Lost Revenue from Compromised Accounts
Customers whose accounts are taken over often leave for good. The trust is broken. Meanwhile, fraudsters using stolen access aren't paying customers - they're extracting value you'll never recover.
Increased Support Costs
Account takeovers flood your support team with password reset requests, fraud investigations, and compensation claims. Each incident costs time and money to resolve.
Reputation Damage
News of compromised accounts spreads quickly. Customers share bad experiences, and potential customers think twice. The brand damage from a credential-stuffing attack can far exceed the direct financial losses.
Impact on Organisations
Early detection of compromised credentials is essential for preventing costly breaches.
Detecting Infected Staff Machines
When employee credentials appear in stealer logs, it's a clear indicator their device has been compromised. Early warning enables rapid response before attackers can use the stolen data.
Blocking Account Takeover
Pre-emptive password resets and session invalidation stop attackers before they can leverage stolen credentials. Every hour of delay increases the risk of a successful breach.
Protecting Revenue
The average cost of a data breach exceeds millions. Continuous credential monitoring costs a fraction of breach response, making it one of the highest-ROI security investments available.
Keep reading
- Find your organisation's stolen credentialsHow DarkStrata detects your staff and customer credentials in stealer logs, notifies the people affected and helps you remediate.
- Ready to go deeper? How infostealer monitoring worksThe full picture: the stealer families active in 2026, what a stealer log contains, and how continuous monitoring catches your exposure inside the 48-hour window.
- Think you've already been compromised?Our step-by-step UK Data Breach Response guide walks you through exactly what to do - for individuals and businesses, including how and when to report to the ICO.
Infostealers: frequently asked questions
Plain answers to the questions security leads ask most about infostealer malware.
What is an infostealer?
An infostealer is malware built to copy saved passwords, session cookies, autofill data, crypto wallets and system details from an infected device, then send them to the attacker. It usually runs once, silently, and takes everything in seconds. The stolen data is packaged into a 'stealer log' and sold or shared on criminal marketplaces and Telegram channels.
How does infostealer malware get onto a computer?
Most infections start with something the victim chose to run: cracked software, game cheats, fake installers, malicious ads or a convincing email attachment. Infostealers are sold as a service, so many criminals distribute them at once. Personal devices used for work are a common route into an organisation, because they sit outside corporate controls.
What is a stealer log?
A stealer log is the bundle of data taken from one infected machine: a folder holding its saved passwords, browser cookies, autofill entries, wallet files and a system profile. Each saved login is paired with the exact site it belongs to, which makes the credentials immediately usable. Logs are traded in bulk, often within 24 to 48 hours of the infection.
Can infostealers bypass multi-factor authentication?
Yes, through session cookies. When you sign in and pass MFA, the browser stores a session cookie that proves you already did. An infostealer copies that cookie, and an attacker who loads it can resume your session without the password or the second factor. Revoking active sessions, not only resetting the password, is what closes this gap.
Which infostealers are most common?
Widely seen families include Lumma, RedLine, Vidar, StealC and Raccoon. New variants and rebrands appear constantly, but their output is similar: a structured log of credentials, cookies and system data. Defending against infostealers means watching for that output, whichever family produced it.
How is an infostealer different from a data breach?
A data breach exposes one company's database, usually old records that often surface months later. An infostealer takes data from a person's own device: every login they saved, for every site, including your organisation's systems and SaaS apps. That data is fresh and often includes live sessions, which makes it the more urgent risk.
How do I know if my organisation's credentials are in stealer logs?
You need a source that collects and searches stealer logs, because they rarely appear in public breach lists. DarkStrata's free domain check searches its infostealer and breach data for credentials tied to your domain and emails you an exposure report. Continuous monitoring then alerts you to new exposures as they surface.
What should I do if a device is infected with an infostealer?
Treat every credential on that device as compromised. Isolate and clean or rebuild the device first. Then, from a clean machine, reset its saved passwords, revoke active sessions and tokens, and re-enrol MFA where needed. Check the affected accounts for unfamiliar sign-ins, and follow your incident response process if work systems were involved.
Protect Your Organisation Today
DarkStrata monitors for your credentials in stealer logs and alerts you before attackers can strike.