Full Report
Advertised on Telegram, Gremlin Stealer is new malware active since March 2025 written in C#. Data stolen is uploaded to a server for publication. The post Gremlin Stealer: New Stealer on Sale in Underground Forum appeared first on Unit 42.
Analysis Summary
# Tool/Technique: Gremlin Stealer
## Overview
Gremlin Stealer is a new piece of malware identified as an information stealer being sold on underground forums, specifically mentioned in the context of Telegram for distribution or commerce. Its primary purpose is to compromise systems and exfiltrate sensitive information.
## Technical Details
- Type: Malware family (Infostealer)
- Platform: Windows (Implied, as most stealers target this platform; specific details not provided in the context excerpt)
- Capabilities: Information stealing (Targeting credentials, browsing data, etc., typical of stealers).
- First Seen: Unknown based on the provided context excerpt, but noted as "New Stealer."
## MITRE ATT&CK Mapping
*(Note: Specific mappings are not detailed in the provided text, so general mappings for information stealers are listed as placeholders based on typical stealer functionality.)*
- TA0010 - Exfiltration
- T1041 - Exfiltration Over C2 Channel
- TA0003 - Persistence
- T1547 - Boot or Logon Autostart Execution
## Functionality
### Core Capabilities
- Data harvesting from the compromised system.
- Aimed at stealing credentials, browser information, and potentially crypto wallets/files common to stealer malware.
### Advanced Features
- The article summary does not detail advanced or unique features, only noting its availability for sale.
## 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: [Not provided in the context]
- Behavioral Indicators: [Likely involves file system enumeration, credential harvesting APIs, and outbound C2 communication.]
## Associated Threat Actors
- Unknown/Unspecified. (It is being sold on underground forums, implying use by various unaffiliated actors or early access customers).
## Detection Methods
- Signature-based detection: [Requires updated signatures based on newly sampled binaries.]
- Behavioral detection: [Monitoring for attempts to read browser databases (e.g., SQLite files), access credential stores, or unusual outbound connections attempting to exfiltrate archives.]
- YARA rules: [Specific YARA rules are not provided in the context.]
## Mitigation Strategies
- Prevention measures: Strong endpoint protection capable of detecting and blocking commodity malware execution; email and web filtering to block paths of initial access.
- Hardening recommendations: Disabling unnecessary services; implementing credential guard; ensuring all software, especially browsers, is up-to-date to prevent exploitation of initial access vulnerabilities.
## Related Tools/Techniques
- Other popular information stealers (e.g., RedLine, Vidar, LummaC2).
- Techniques associated with initial access and execution common to malware sold on forums.