Full Report
2025-02-27 • Fortinet • Pei Han Liao • win.valley_rat, win.winos Open article on Malpedia
Analysis Summary
# Threat Actor: Winos (Implied)
## Attribution & Identity
This analysis is based on activity related to malware named "Winos 4.0" and an associated file/tool named "win.valley\_rat" and "win.winos". Specific attribution to a named threat group is not provided in the description, but the activity targets Taiwan.
## Activity Summary
The primary activity described is the spread of **Winos 4.0** malware. This malware is being distributed via a social engineering technique involving **impersonation of official email** targeting users in Taiwan.
## Tactics, Techniques & Procedures
- Initial Access via **Email Impersonation/Social Engineering**.
- Use of malware variants including **Winos 4.0**, **win.valley\_rat**, and **win.winos**.
## Targeting
- Sectors: Undetermined from description, but generally targets users via email.
- Geography: **Taiwan**.
- Victims: Users receiving the malicious emails.
## Tools & Infrastructure
- Malware Families: **Winos 4.0**, **win.valley\_rat**, **win.winos**.
- Infrastructure: Not specified in the description.
## Implications
This actor is employing targeted social engineering attacks leveraging official email impersonation to distribute custom malware (Winos 4.0) specifically against users located in Taiwan. This suggests a potentially localized espionage or data theft motivation.
## Mitigations
- Enhanced user training on identifying **email impersonation and social engineering** attempts.
- Strict filtering and inspection of incoming email attachments and links.
- Monitoring for the presence of Winos variants (Winos 4.0, win.valley\_rat, win.winos).