Infostealer Malware Explained: How It Works, Real-World Examples, and How to Stay Safe

Introduction

In an era where data drives decisions, business growth, and daily communications, cybercriminals have found countless ways to exploit it. One of the most pervasive and rapidly evolving threats is infostealer malware—a type of malicious software designed to silently harvest and transmit sensitive data to attackers.

Unlike ransomware, which demands attention and payment, infostealers thrive in the shadows. They infiltrate systems quietly and exfiltrate usernames, passwords, financial info, browser cookies, and much more—leaving victims unaware until damage is done.

This post dives deep into what infostealers are, how they operate, showcases notable real-world examples, and offers practical ways to defend against them.

What is Infostealer Malware?

Infostealers (or information stealers) are specialized forms of malware that collect and transmit sensitive data from infected machines. They are widely used in credential harvesting, identity theft, and initial access sales (where attackers sell stolen credentials on dark web marketplaces for others to exploit).

These threats are often part of broader cybercrime campaigns and can affect individuals, SMBs, and large enterprises alike.

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How Infostealers Work

Step-by-Step Breakdown:

1. Infection Vector

   Infostealers are typically delivered via:

   • Phishing emails with malicious attachments or embedded links.

   • Malvertising (ads that redirect users to exploit kits or malware downloads).

   • Drive-by downloads from compromised or malicious websites.

   • Trojanized software or fake installers, especially cracked or pirated tools.

     
     

     

     
     

2. Execution and Data Harvesting

   After installation, the malware:

   • Scans browsers (Chrome, Firefox, Edge) for saved credentials, cookies, autofill data.

   • Captures screenshots or clipboard contents.

   • Scans for cryptocurrency wallet files.

   • Extracts FTP, VPN, or email client credentials.

     
     

3. Data Exfiltration

   All stolen data is typically compressed and sent to a Command & Control (C2) server via HTTP, FTP, or Telegram bots.

   
   

   

   
   

Real-World Infostealer Examples

🕵️‍♂️ 1. RedLine Stealer

• Description: Sold on underground forums as a MaaS (Malware-as-a-Service).

• Targets: Browser data, passwords, credit cards, and cryptocurrency wallets.

• Spread through: Cracked software, phishing emails, malvertising.

• Notable Campaigns: Frequently used in initial access brokers' operations.

  
  

🧊 2. Raccoon Stealer

• Description: Widely used for stealing browser credentials, system info, and crypto wallets.

• Unique Feature: Delivered through fake software updates and phishing websites.

• Usage: Known to be user-friendly for attackers; often seen bundled with other malware loaders.

  
  

🎭 3. Vidar Stealer

• Description: Forked from Arkei Stealer; customizable and widely used.

• Capabilities: Steals browser autofill data, cookies, documents, and messaging app data (Telegram, Discord).

• Distribution: Google Ads abuse, fake installers (e.g., pirated Photoshop).

  
  

🐍 4. Lumma Stealer (aka LummaC2)

• Description: A modern stealer with advanced obfuscation.

• Targets: Email clients, VPNs, gaming accounts, and crypto extensions.

• Notes: Regularly updated to evade detection and used by threat actors targeting financial institutions.

  
  

🛠️ 5. MetaStealer

• Focus: Corporate credentials, especially Apple macOS systems.

• Tactics: Distributed through fake job offers or business communications targeting HR and finance departments.

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Prevention and Protection: How to Defend Against Infostealers

🔒 1. Use a Reputable Antivirus/EDR Solution

Install and maintain up-to-date antivirus software that includes behavioral detection capabilities. EDR (Endpoint Detection & Response) tools can offer additional protection with real-time monitoring and threat response.

🔐 2. Enable Multi-Factor Authentication (MFA)

Even if credentials are stolen, MFA prevents unauthorized access by requiring a second authentication method like a phone prompt or security key.

🧠 3. User Awareness and Training

Educate users on phishing red flags:

• Suspicious sender addresses

• Unexpected attachments

• Urgent tone or fake branding

Use simulated phishing campaigns to build resilience.

🚫 4. Avoid Cracked or Pirated Software

Illegal software is a leading delivery method for infostealers. Use only verified software from official sources.

🔁 5. Regularly Rotate and Strengthen Passwords

Use complex, unique passwords for each account. Rotate them periodically and avoid browser-stored credentials.

🧰 6. Use a Password Manager

Tools like Bitwarden, 1Password, or LastPass offer secure vaults for storing and generating strong passwords—away from the browser's easy reach.

🔄 7. Keep Systems and Apps Updated

Outdated software is vulnerable to exploits that infostealers and other malware can leverage. Set updates to automatic wherever possible.

🧑‍💻 8. Monitor for Signs of Exfiltration

Use tools like network monitoring and SIEMs (Security Information and Event Management) to detect unusual outbound traffic or system behavior.

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Real-World Infostealer Examples with IOCs

*IOC = Indicators of compromise

🕵️‍♂️ 1. RedLine Stealer

A top-selling infostealer on underground forums, RedLine is known for its ease of use and versatility.

IOCs (as of recent campaigns):

• Common Filenames:

  • Updater.exe, Client32.exe, ChromeUpdate.exe

• File Hashes (SHA256):

  • cd56a2ff1d812e6dd2040a0e7df77571b02c985c239fa3cb43f8f82cfba5b9e1

  • 1e4edb8619fdcd22dfdf0c6b331e06bd4e9357d70db6e28a774a21755e2944e2

• Domains/C2 URLs:

  • hxxp://redlinehost.xyz/api

  • hxxp://185.225.74.45:4505/api/post

• IPs:

  • 185.225.74.45, 94.103.80.86

• Behavioral Patterns:

  • Enumerates browser credential stores

  • Connects over HTTP/HTTPS to C2

  • Drops DLLs in %AppData% or %Temp%

    
    

🧊 2. Raccoon Stealer

Known for user-friendly controls and frequent updates. Often distributed via fake installers or phishing campaigns.

IOCs:

• Filenames:

  • setup.exe, update_win.exe, winstart.exe

• Hashes:

  • 3f4df80c598b41b08e99bfcdebd208fddf5f88d0e07e14cfb6bd1df5ff36f712

• Domains:

  • hxxp://raccoon-top[.]xyz, hxxp://78.128.113.214/api/upload

• IPs:

  • 78.128.113.214, 45.9.148.90

• Behavioral Traits:

  • Uses Telegram bot APIs for exfiltration

  • Collects browser and system data

  • Deletes itself post-exfiltration

    
    

🎭 3. Vidar Stealer

Highly modular and can be customized via configuration files by attackers.

IOCs:

• Executable Names:

  • vidar.exe, winhost.exe, loader.exe

• Sample Hashes:

  • 26e8b50a028fe2c2fc8ac6492c4f53d1ae3743c8965f7dd4c1eb30517119a34b

• Known C2s:

  • hxxp://vidarc2[.]com, hxxp://37.120.250.33/

• IPs:

  • 37.120.250.33, 185.154.53.140

• TTPs (Tactics, Techniques, Procedures):

  • Uses HTTP POST for data exfiltration

  • Can load secondary payloads

  • Stores stolen data in ZIPs before upload

    
    

🐍 4. Lumma Stealer

Modern, fast-evolving stealer targeting financial platforms and gaming users.

IOCs:

• Filenames:

  • GameUpdate.exe, Lumma32.exe, client.exe

• SHA256 Hashes:

  • 9f63b07df88efb5894b61d0dc4b33aa6a5e0ff9ce9d3cce8e6cf75c82f5d20a1

• C2 Domains:

  • hxxp://lumma[.]dev, hxxp://lumma-log[.]cc

• IPs:

  • 89.185.85.35, 147.78.66.31

• Typical Actions:

  • Focuses on cryptocurrency browser extensions

  • Steals session tokens from browsers

  • Encrypts local ZIP archive of stolen data

Conclusion

Infostealer malware is stealthy, sophisticated, and a growing threat across the digital landscape. From RedLine to Raccoon Stealer, these malicious tools don’t just aim to disrupt—they aim to profit quietly from your sensitive data.

Whether you're running a business, managing IT infrastructure, or browsing casually, the best defense is proactive cybersecurity hygiene. Educate, update, and secure—because your information is worth more than you think.

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