Full Report
Attacks using this ransomware have displayed consistent TTPs and grown steadily since 2023.
Analysis Summary
# Tool/Technique: Medusa Ransomware and Associated Tools
## Overview
Medusa is a ransomware variant associated with the threat actor Spearwing (and its affiliates). The attack chain consistently utilizes a specific set of commercial and open-source tools for pre-deployment activities, defense evasion, lateral movement, and data exfiltration. TTPs have remained highly consistent since its emergence in 2023, suggesting a controlled playbook rather than a typical RaaS model.
## Technical Details
- Type: Malware Family (Ransomware) and Toolset
- Platform: Windows
- Capabilities: File encryption, process termination, self-deletion, data exfiltration.
- First Seen: Active since 2023.
## MITRE ATT&CK Mapping
The following mappings are derived from the composite TTPs described for Medusa attacks:
- **TA0002 - Execution**
- T1059 - Command and Scripting Interpreter
- T1059.003 - Windows Command Shell
- **TA0005 - Defense Evasion**
- T1218 - Signed Binary Proxy Execution
- T1218.011 - Built-in Virtualization (**BYOVD Technique** mentioned for disabling security)
- T1036 - Masquerading
- T1070 - Indicator Removal
- T1070.004 - File Deletion (Self-deletion of ransomware)
- **TA0008 - Lateral Movement**
- T1021 - Remote Services
- T1021.001 - Remote Desktop Protocol (RDP)
- **TA0011 - Collection**
- T1005 - Data from Local System (Accessing `ntds.dit`)
- **TA0010 - Exfiltration**
- T1041 - Exfiltration Over C2 Channel (Implied by general exfiltration via Rclone/Robocopy)
- **TA0004 - Privilege Escalation**
- T1548.002 - Bypass User Account Control (**KillAV/KillAVDriver** implies privilege abuse for kernel interaction)
## Functionality
### Core Capabilities (Medusa Ransomware)
- File Encryption: Encrypts files on victim machines, appending the `.medusa` extension.
- Ransom Note: Drops a note named `_!READ_ME_MEDUSA!!!.txt` in all encrypted directories.
- Self-Deletion: The ransomware binary (`gaze.exe` in the observed case) deletes itself after execution, complicating forensic analysis.
- Process Termination: Decodes a list of services and processes using key `0x2e` and terminates them using `net stop` and `taskkill /F /IM /T`.
- Exclusions: Does not encrypt files with extensions `.dll`, `.exe`, `.lnk`, `.MEDUSA`, nor content in specific system/program folders.
### Advanced Features
- **Defense Impairment:** Deployment of an **AVKiller binary and driver** (potentially leveraging known BlackCat drivers in early instances) to terminate security processes before encryption.
- **TTP Consistency:** Strict adherence to a playbook involving pre-staging tools, use of specific deployment mechanisms (PDQ Deploy), and consistent credential dumping steps.
- **Ransom Negotiation:** Demands vary; initial period is 10 days, with an additional $10,000 daily penalty for extensions. Attackers provide data screenshots as proof of compromise.
## Indicators of Compromise
- File Hashes: (Not explicitly listed in the summary text; requires external context.)
- File Names:
- Ransomware Binary: `gaze.exe` (observed instance)
- Ransom Note: `_!READ_ME_MEDUSA!!!.txt`
- Staged tools often found in: `CSIDL_PROFILE\\documents`
- Registry Keys: (Not explicitly listed in the summary text.)
- Network Indicators: (None explicitly listed in the summary text, except for RDP/network scanning activity).
- Behavioral Indicators:
- Execution of `wmic shadowcopy call create Volume='C:'` (or similar `vssadmin create shadow`) followed by later deletion.
- Use of legitimate administration tools (PDQ Deploy, RDP) for lateral movement and encryption deployment.
- Use of **BYOVD** technique to load drivers to terminate security software.
## Associated Threat Actors
- Spearwing (Primary group)
- Affiliates of Spearwing (Implied by RaaS structure investigation)
## Detection Methods
- Signature-based detection: Signatures for the ransomware binary (`gaze.exe`, etc.) and specific driver files (**KillAV**).
- Behavioral detection: Monitoring for the mass execution of legitimate tools (PDQ Deploy, Rclone, RoboCopy) coupled with credential access (`ntds.dit` access) and security product termination attempts.
- YARA rules: Potential rules on process termination strings or the specific list of services/processes targeted for termination.
## Mitigation Strategies
- Patching and Software Management: Strict control over software deployment via **PDQ Deploy** to limit unauthorized executables on endpoints.
- Restrict Administrative Tools: Limit use of RDP, PsExec, and public deployment software unless strictly controlled.
- Credential Security: Implement measures to prevent access to `ntds.dit` (e.g., restricting local admin rights, applying LAPS).
- Driver Enforcement: Implement strict Kernel driver signing policies to prevent the loading of unauthorized kernel drivers like those used by **KillAV**.
- Backup Integrity: Ensure backups are isolated and protected from modification/deletion by ransomware activities involving VSS shadow copies.
## Related Tools/Techniques
- **AnyDesk, Mesh Agent, SimpleHelp:** Other remote access tools used alongside this malware chain.
- **Navicat, Rclone, RoboCopy:** Tools used for data staging and exfiltration.
- **PDQ Deploy, PDQ Inventory:** Legitimate tools abused for mass deployment and reconnaissance.
- **BlackCat/Noberus Tools:** Early Medusa attacks showed similarities in drivers used (though a confirmed link remains unproven).