Legion Loader: Technical Analysis and Removal Guide

Legion Loader is a sophisticated malware dropper first discovered in 2025 that serves as a delivery mechanism for multiple secondary payloads including trojans, ransomware, information stealers, and malicious browser extensions. Distributed primarily through fake CAPTCHA interfaces, deceptive websites, and bundled software, Legion Loader employs advanced evasion techniques including API hashing, shellcode execution, and multi-stage obfuscation to avoid detection. Once installed, it creates a persistent infection capable of installing multiple malicious payloads that can monitor browsing activity, steal sensitive data, abuse system resources, and cause significant financial damage. This comprehensive analysis examines Legion Loader’s technical characteristics, infection chain, associated threats, and provides detailed removal instructions.

Technical Analysis of Legion Loader

Legion Loader represents a significant evolution in malware dropper functionality, employing sophisticated evasion techniques and multi-stage infection mechanisms. Security researchers at Netskope have identified this malware as particularly dangerous due to its modular architecture and ability to distribute a wide variety of malicious payloads. The malware’s primary function is to establish persistence on infected systems and facilitate the download and execution of additional malicious software.

What makes Legion Loader especially concerning is its sophisticated obfuscation techniques that help it evade detection by security solutions. The loader employs multiple layers of encryption, shellcode execution, and API hashing to obscure its functionality and hide its malicious intent from security analysis tools.

Infection Chain Analysis

Legion Loader’s infection chain consists of multiple sophisticated stages:

1. Initial Access: Users are tricked into interacting with fake CAPTCHA interfaces or downloading deceptive PDFs from websites like file-connection-all-ez.com
2. First Stage: Execution of obfuscated PowerShell commands that download and execute the next stage payload
3. Shellcode Loader: A deobfuscated shellcode buffer containing critical information including:
   • XTEA encryption key for payload decryption
   • API hashing table using CRC32 algorithm
   • Process hollowing components targeting explorer.exe
4. Process Hollowing: Legion Loader injects its payload into a legitimate Windows process (explorer.exe)
5. Secondary Payload Delivery: The fully activated Legion Loader begins downloading and installing additional malware

Advanced Obfuscation Techniques

Legion Loader employs multiple layers of sophisticated obfuscation to evade detection:

• Multi-Stage PowerShell Deobfuscation: The initial PowerShell script undergoes several deobfuscation steps:
  • Character replacement operations
  • Multiple Base64 decoding operations
  • XOR decryption using both static and multi-byte keys
• API Hashing: Instead of directly calling Windows API functions by name (which would be easily detectable), Legion Loader implements an API hashing technique using CRC32 as the algorithm
• XTEA Encryption: The main payload is encrypted using the XTEA algorithm with the key “25 A9 79 7B 42 15 C7 C8 F3 DE 7E 25 DF 46 37 5F”
• Process Hollowing: The malware creates a legitimate Windows process in a suspended state, replaces its memory with malicious code, and resumes execution to appear as legitimate activity

Malicious Browser Extension Payload

One of Legion Loader’s most concerning payloads is a sophisticated malicious browser extension:

• Deceptive Appearance: Masquerades as legitimate extensions like “Save to Google Drive”
• String Obfuscation: Uses byte arrays instead of plain text strings to avoid detection
• Multiple Browser Targeting: Specifically targets Google Chrome, Microsoft Edge, Brave, and Opera browsers
• Browser Modifications: Modifies the browser’s Secure Preferences file to enable developer mode and install the malicious extension
• Extensive Permissions: Requests extensive browser permissions to access sensitive data
• Cryptocurrency Monitoring: Contains specific functionality to monitor Bitcoin-related activities

Legion Loader Capabilities

Legion Loader’s extensive capabilities make it a significant threat to infected systems:

• Secondary Malware Deployment: Downloads and executes additional malware, including:
  • Remote access trojans (RATs) for complete system control
  • Ransomware that encrypts user files and demands payment
  • Information stealers that extract sensitive data
  • Cryptocurrency miners that consume system resources
• Browser Data Theft: The malicious browser extension can:
  • Steal cookies, browsing history, and saved passwords
  • Monitor form submissions including login credentials
  • Track cryptocurrency-related activities
  • Exfiltrate clipboard contents
• System Persistence: Creates registry modifications to ensure continued operation after system restarts
• Anti-Analysis Techniques: Employs multiple methods to hinder analysis and detection by security tools

Distribution Methods

Legion Loader utilizes a variety of sophisticated distribution methods to maximize infection rates. Recent research by Netskope has identified several primary distribution channels, with particular emphasis on fake CAPTCHA and verification interfaces that have proven highly effective at tricking users into executing malicious code.

Fake CAPTCHA Interfaces

A primary distribution method for Legion Loader involves sophisticated fake CAPTCHA interfaces designed to mimic legitimate verification systems:

• Cloudflare Turnstile Imitation: The malware authors create convincing replicas of the Cloudflare Turnstile verification system
• “I’m not a robot” Buttons: Deceptive interfaces featuring the familiar “I’m not a robot” button that users are conditioned to click
• PDF Document Lures: The fake CAPTCHAs often appear on websites claiming to offer PDF documents, particularly user manuals for various products
• SEO Poisoning: Attackers utilize search engine optimization techniques to ensure their malicious sites appear in search results for common queries, especially for user manuals and PDF documents

When users interact with these fake CAPTCHA interfaces, they unwittingly initiate the Legion Loader infection chain. This distribution method is particularly effective because it exploits users’ familiarity with legitimate CAPTCHA systems and their desire to access specific content.

Deceptive Websites

Legion Loader is commonly distributed through websites specifically designed to appear legitimate while delivering malicious content:

• PDF Document Sites: Websites like file-connection-all-ez.com that claim to offer PDF documents but actually deliver malware
• Software Download Portals: Fake software distribution sites like appsuccess[.]monster that offer seemingly legitimate applications
• Technical Documentation Sites: Pages claiming to offer technical manuals, user guides, or other documentation
• Tutorial Websites: Sites offering tutorials or guides with deceptive download buttons

These deceptive websites often include step-by-step instructions designed to guide users through the infection process. For example, they might provide detailed instructions on how to “download a file using curl on Windows” or other seemingly legitimate procedures that actually facilitate malware execution.

Potentially Unwanted Applications (PUAs)

Legion Loader is also distributed through potentially unwanted applications that act as initial droppers:

• Temeliq Ultra Touch: A PUA that serves as a dropper for Legion Loader, distributed through deceptive websites
• Other PUA Droppers: Similar applications including Tao Raiqsuv Utils, Klio Verfair Tools, and others that facilitate Legion Loader installation
• Bundled Software: Legion Loader components bundled with seemingly legitimate free software offerings
• Deceptive Installers: Software installers that include hidden components that download and install Legion Loader

Symptoms of Infection

Legion Loader infections manifest through various symptoms that can help identify its presence on a system. While the malware itself attempts to operate stealthily, the multiple secondary infections it facilitates often produce more noticeable indicators. Early detection is crucial for preventing the significant damage that can result from a full infection chain.

Primary Legion Loader Symptoms

• Unexplained Browser Extensions: The appearance of unknown browser extensions, particularly those masquerading as legitimate services like “Save to Google Drive”
• Multiple Malware Infections: The sudden presence of various types of malware that weren’t previously on the system
• Modified Browser Settings: Changes to browser preferences, particularly enabling of developer mode or modified security settings
• Unexpected Process Activity: Unusual activity from legitimate Windows processes like explorer.exe, including unexpected network connections
• Persistence Mechanisms: New startup items or scheduled tasks that didn’t exist before

Secondary Infection Symptoms

The secondary payloads deployed by Legion Loader produce additional symptoms:

• System Performance Impact:
  • Significant slowdown in system performance
  • High CPU and memory usage, especially when the system should be idle
  • Overheating and increased fan activity due to resource-intensive cryptocurrency mining
• Privacy and Security Breaches:
  • Unexplained account breaches or unauthorized access to online services
  • Stolen credentials and unauthorized financial transactions
  • Unusual browser behavior when visiting banking or cryptocurrency websites
• Ransomware Indicators:
  • Encrypted files with unusual extensions
  • Ransom notes appearing on the desktop or in affected folders
  • Inability to access personal files and documents
• Trojan Activity:
  • Webcam activation without user permission
  • Unusual outbound network connections
  • System changes occurring without user action

Legion Loader Removal Instructions

Removing Legion Loader and its associated payloads requires a comprehensive approach due to the malware’s sophisticated persistence mechanisms and the multiple secondary infections it facilitates. The removal process must address both the primary Legion Loader components and all secondary payloads to ensure complete remediation.

Step 1: Boot into Safe Mode with Networking

Starting in Safe Mode helps prevent malware from fully loading during the cleanup process:

1. Windows 10 and 11:
   • Click the Start button
   • Click the Power button
   • Hold the Shift key and click Restart
   • Select Troubleshoot → Advanced options → Startup Settings → Restart
   • After restart, press F5 to select “Safe Mode with Networking”
2. Windows 7:
   • Restart your computer
   • As it’s starting up, press the F8 key repeatedly until the Advanced Boot Options menu appears
   • Select “Safe Mode with Networking” using the arrow keys and press Enter

Step 2: Terminate Malicious Processes

1. Press Ctrl+Shift+Esc to open Task Manager
2. Click on the “Processes” tab
3. Look for suspicious processes with unusual names or processes consuming excessive resources
4. Right-click on each suspicious process and select “End task”
5. Pay special attention to any instances of explorer.exe that have unusual network activity

Step 3: Remove Malicious Browser Extensions

Legion Loader commonly installs malicious browser extensions that need to be removed from all browsers:

For Google Chrome:

1. Open Chrome and type chrome://extensions/ in the address bar
2. Look for suspicious extensions, particularly those with names like “Save to Google Drive” that you didn’t install
3. Click the “Remove” button for each suspicious extension
4. Additionally, type chrome://settings/resetProfileSettings in the address bar
5. Click “Reset settings” to restore Chrome to its default state

For Microsoft Edge:

1. Open Edge and type edge://extensions/ in the address bar
2. Remove any suspicious extensions
3. Go to edge://settings/resetSettings
4. Click “Restore settings to their default values”

For Mozilla Firefox:

1. Open Firefox and click the menu button (three lines) in the top-right corner
2. Select “Add-ons and themes”
3. In the Extensions tab, remove any suspicious extensions
4. Go to the menu again, select “Help” and then “Troubleshooting Information”
5. Click “Refresh Firefox” button

For Brave:

1. Open Brave and type brave://extensions/ in the address bar
2. Remove any suspicious extensions
3. Type brave://settings/reset in the address bar
4. Click “Restore settings to their original defaults”

Step 4: Check and Clean Startup Items

1. Press Win+R to open the Run dialog
2. Type msconfig and press Enter
3. Go to the “Startup” tab
4. Look for suspicious entries and uncheck them
5. Click “Apply” and “OK”

Step 5: Check Scheduled Tasks

1. Press Win+R to open the Run dialog
2. Type taskschd.msc and press Enter
3. Browse through the Task Scheduler Library
4. Look for recently created or suspicious tasks
5. Right-click on suspicious tasks and select “Delete”

Step 6: Scan with Anti-Malware Software

For comprehensive removal, we recommend using specialized anti-malware software:

1. Download and Install Trojan Killer:
   • Download Trojan Killer from a clean, uninfected computer
   • Transfer it to the infected computer using a USB drive if necessary
2. Run a Full System Scan:
   • Launch Trojan Killer and perform a full system scan
   • Allow the software to detect and quarantine all threats
3. Remove Detected Threats:
   • Review the scan results and remove all detected threats
   • Pay special attention to threats detected in the Windows system directory and browser directories
4. Restart Your Computer:
   • Restart to complete the removal process
5. Run a Second Scan:
   • After restarting, run another scan to ensure all threats have been removed

Step 7: Verify Complete Removal

After following the above steps, verify that Legion Loader has been completely removed:

1. Check System Performance: Ensure that system performance has returned to normal, with no unexplained high CPU or memory usage
2. Verify Browser Extensions: Confirm that no suspicious browser extensions remain
3. Check for New Files: Ensure no suspicious new files are being created
4. Monitor Network Activity: Check for unusual network connections or data transfers

Prevention Measures

Preventing Legion Loader infections requires a combination of security best practices, awareness of distribution methods, and proactive protection measures. The sophisticated nature of this threat means that a multi-layered security approach is essential for effective prevention.

CAPTCHA and Verification System Awareness

• Verify Website Legitimacy: Before interacting with any CAPTCHA or verification system, verify that you’re on a legitimate website by checking the URL
• Be Suspicious of PDF Download Sites: Exercise extreme caution with websites offering PDF documents, especially user manuals
• Examine CAPTCHA Behavior: Legitimate CAPTCHAs typically don’t initiate downloads or request unusual permissions
• Use Official Sources: Whenever possible, download manuals and documentation directly from manufacturers’ official websites

System Security Measures

• Keep Software Updated: Regularly update your operating system, browsers, and applications to patch security vulnerabilities
• Use Advanced Security Software: Implement reputable security solutions with real-time protection capabilities
• Enable User Account Control (UAC): Keep UAC enabled to prompt for permission before making system changes
• Regular System Backups: Maintain regular backups of important data to minimize the impact of ransomware attacks

Browser Security Practices

• Disable Automatic Downloads: Configure your browser to ask before downloading files
• Use Web Protection Extensions: Consider using legitimate browser extensions that block malicious websites
• Review Extension Permissions: Carefully review the permissions requested by browser extensions before installation
• Disable Developer Mode: Unless needed for legitimate purposes, keep developer mode disabled in browsers

User Awareness and Education

• Recognize Social Engineering: Be aware of common social engineering tactics used to distribute malware
• Exercise Caution with Downloads: Only download files from trusted, verified sources
• Verify Before Execution: Scan downloaded files with security software before execution
• Be Wary of Free Software: Exercise extra caution with free software, which often bundles unwanted applications

Conclusion

Legion Loader represents a sophisticated evolution in malware delivery mechanisms, employing advanced evasion techniques and a multi-stage infection chain to distribute various malicious payloads. Its distribution through fake CAPTCHA interfaces and deceptive PDF download sites presents a significant challenge to users seeking legitimate content online. The malware’s ability to deploy multiple secondary infections, including trojans, ransomware, information stealers, and malicious browser extensions, makes it a particularly dangerous threat.

The technical sophistication of Legion Loader, including its use of API hashing, XTEA encryption, and process hollowing techniques, demonstrates the advanced capabilities of modern malware authors. These evasion methods allow it to bypass many traditional security measures and establish persistence on infected systems.

Protecting against Legion Loader requires a comprehensive security approach that includes awareness of its distribution methods, implementation of robust system security measures, and the use of advanced security solutions. If infection occurs, the detailed removal instructions provided in this guide can help eliminate Legion Loader and its associated threats. By combining effective prevention strategies with thorough removal techniques, users can safeguard their systems against this evolving and dangerous malware threat.

For more information about protecting against malware threats, explore our guides on ransomware protection, browser security best practices, and safe downloading practices.