Full Report
Administrators of a Telegram channel named CoderSharp have been advertising Gremlin Stealer since March 2025
Analysis Summary
# Tool/Technique: Gremlin Stealer
## Overview
Gremlin Stealer is a newly identified type of information stealer malware, written in C#, designed to compromise Windows systems. It is advertised and distributed primarily via the Telegram messaging platform by threat actors associated with the "CoderSharp" Telegram channel. Its primary purpose is to steal sensitive data from various applications on the victim's machine and exfiltrate it to a dedicated web server for publication.
## Technical Details
- Type: Malware family (Infostealer)
- Platform: Windows
- Capabilities: Steals data from browsers, captures screenshots, collects clipboard data, and targets local disk contents. It has been noted it can bypass Chrome cookie V20 protection.
- First Seen: Advertised since mid-March 2025.
## MITRE ATT&CK Mapping
*Note: Exact mappings are inferred based on described functionality as the article does not explicitly list TTPs.*
- **TA0009 - Collection**
- T1119 - Data from Local System (Inferred from stealing browser, clipboard, and local disk data)
- T1113 - Screen Capture
- **TA0010 - Exfiltration**
- T1041 - Exfiltration Over C2 Channel (Inferred from uploading data to a web server)
## Functionality
### Core Capabilities
- Steals data from installed web browsers (e.g., credentials, cookies).
- Captures the contents of the local device clipboard history.
- Takes screenshots of the user's desktop environment.
- Searches for and collects files from the local disk.
### Advanced Features
- Written in C#, suggesting adaptability or use of common .NET capabilities.
- Specifically mentioned capability to bypass Chrome cookie V20 protection.
- Its build process is self-contained, meaning it does not pull additional components from the internet post-build.
- Exfiltrates collected data to the attacker's web server for centralized access and publication.
## Indicators of Compromise
- File Hashes: [Not provided in the context.]
- File Names: [Not provided in the context.]
- Registry Keys: [Not provided in the context.]
- Network Indicators: Uploads data to an attacker-controlled web server (specific indicators not detailed).
- Behavioral Indicators: High volume data transfer to an external web server; processes attempting to read browser storage files or capture screen data.
## Associated Threat Actors
- Threat actors advertising on the Telegram channel named "CoderSharp."
## Detection Methods
- Signature-based detection: Signatures could target the known C# compilation profile or specific strings associated with the stealer.
- Behavioral detection: Monitoring for processes exhibiting file system access across multiple user profiles, attempts to read browser databases (e.g., SQLite files), and unauthorized external data uploads.
- YARA rules: Could be developed based on unique strings or resource sections within the malware binary.
## Mitigation Strategies
- Implement strict outbound firewall rules to limit traffic only to trusted destinations, potentially blocking exfiltration to unknown web servers.
- Use endpoint security solutions capable of detecting behavioral patterns associated with infostealers (e.g., mass file reading, screen capturing).
- Configure defenses to monitor and alert on suspicious activity related to Chrome cookie stores or clipboard access by unknown processes.
- User training regarding social engineering attacks, especially those distributing illicit software or files via platforms like Telegram.
## Related Tools/Techniques
- Other Infostealers (e.g., Vidar, RedLine, Raccoon Stealer).
- Stealers utilizing Telegram for distribution or advertising.