Full Report
FortiGuard Labs details Chaos-C++, a ransomware variant using destructive encryption and clipboard hijacking to amplify damage and theft. Read more.
Analysis Summary
# Tool/Technique: Chaos-C++ Ransomware
## Overview
Chaos-C++ is an evolved variant of the Chaos ransomware, notably rewritten in C++ rather than its predecessor's .NET implementation. Its primary purpose is destructive encryption of victim files, amplified by clipboard hijacking for cryptocurrency theft, marking an evolution toward more aggressive extortion tactics.
## Technical Details
- Type: Malware family | Ransomware
- Platform: Microsoft Windows
- Capabilities: Destructive file encryption, clipboard hijacking/replacement, system recovery feature disabling, speed-optimized operations.
- First Seen: Article dated October 08, 2025, detailing the C++ variant's evolution during 2025.
## MITRE ATT&CK Mapping
*Note: Specific mappings are inferred based on described behaviors.*
- **TA0001 - Initial Access**
- T1566 - Phishing (Implied by downloader distribution, though not explicitly detailed)
- **TA0002 - Execution**
- T1204.002 - User Execution: Malicious File
- **TA0003 - Privilege Escalation**
- T1548.002 - Bypass User Account Control (Implied by attempts to run commands requiring admin rights)
- **TA0005 - Defense Evasion**
- T1055 - Process Injection (Implied by payload execution stealth)
- T1070.004 - File Deletion (Used for system recovery files)
- **TA0009 - Collection**
- T1115 - Clipboard Data (Directly mentioned via hijacking)
- **TA0011 - Command and Control**
- T1071 - Application Layer Protocol (Likely used for ransom note communication, though C2 details are absent)
- **TA0012 - Impact**
- T1486 - Data Encrypted for Impact
- T1490 - Inhibit System Recovery (Disabling VSS, shadow copies, recovery options)
## Functionality
### Core Capabilities
- **Download & Execution:** Delivered via a downloader masquerading as "System Optimizer v2.1." The downloader writes the payload to `%TMP%\\\\svc[XXXX].tmp` and executes it stealthily using `CREATE_NO_WINDOW` or `cmd.exe /c start /b`.
- **Self-Protection & Stealth:** Renames its console window title to `svchost.exe` and creates a unique mutex (`SvcHost_Mutex_7z459ajrk`) to ensure single instance operation.
- **Persistence Check:** Checks for `%APPDATA%\READ_IT.txt` to determine if it has already run; if present, it enters clipboard monitoring mode instead of full encryption.
- **Destructive Encryption:** Uses destructive encryption techniques, including deleting the contents of very large files instead of encrypting them to accelerate the attack.
### Advanced Features
- **System Recovery Disablement:** When run with administrative privileges (verified by attempted creation/deletion of `C:\WINDOWS\test.tmp`), it executes commands to disable recovery mechanisms:
- `vssadmin delete shadows /all /quiet`
- `wmic shadowcopy delete`
- `bcdedit /set {default} bootstatuspolicy ignoreallfailures`
- `bcdedit /set {default} recoveryenabled no`
- `wbadmin delete catalog -quiet`
- **Clipboard Hijacking:** Monitors the system clipboard and automatically swaps any copied Bitcoin addresses with an attacker-controlled wallet address, facilitating covert theft of cryptocurrency intended for other targets.
## Indicators of Compromise
- File Hashes:
- **Downloader SHA256:** `2fb01284cb8496ce32e57d921070acd54c64cab5bb3e37fa5750ece54f88b2a4`
- **Payload SHA256 (Chaos-C++_type3):** `19f5999948a4dcc9b5956e797d1194f9498b214479d2a6da8cb8d5a1c0ce3267`
- **Other Payload Hashes (SHA256):** `f200ea7ccc5c9b0eaada74046551ed18a3a9d11c9e87999b25e6b8ee55857359`, `f4b5b1166c1267fc5a565a861295a20cf357c17d75418f40b4f14b094409d431`, `9521a154b06743fcb3a24b6b61ae0b4cbd1f1ba74d3d9cd9110042082d0b1d5c`, `5d3fcf6532c9ee5778753c3f13e71d1e3b157b49e56133bdff5d04d6e6d6c8be`, `fe717bab60f1b03012b1e6287e3f3725f1ad5163897041b824024aedabb7c46d`, `76fde847037ca79c8e897fac9d80567efc4ec3a193ec3d8ae9c9fcd9e1ac4939`, `bbf9ebbfd93306108299e54ecbfb59bb9433eeb34f89cef61864f4e87640eaf0`
- File Names:
- Downloader disguise: `System Optimizer v2.1`
- Infected log file: `%TMP%\sysopt.log`
- Payload locations: `%TMP%\\\\svc[XXXX].tmp`
- Ransom note (implied, though filename not explicitly stated): Presence of `%APPDATA%\READ_IT.txt` indicates prior run.
- Registry Keys: None explicitly detailed in the primary execution flow, other than process naming/hiding.
- Network Indicators: None provided in the context.
- Behavioral Indicators:
- Creation of mutex: `SvcHost_Mutex_7z459ajrk`.
- Attempt to create file at `C:\WINDOWS\test.tmp` to check for elevated permissions.
- Modification of system recovery settings via OS commands.
- Continuous monitoring and replacement of clipboard contents.
## Associated Threat Actors
- Chaos Ransomware Family (This specific C++ variant is the evolution of this family).
## Detection Methods
- Signature-based detection (FortiGuard AV Signatures listed):
- `W64/Filecoder.XM!tr.ransom`
- `W64/Filecoder.MLKGEBH!tr.ransom`
- `W64/Imps.1!tr.ransom`
- Behavioral detection of privilege escalation attempts followed by execution of VSS/Bcdedit deletion commands.
- Detection of hidden log files in `%TMP%`.
## Mitigation Strategies
- Maintain up-to-date security solutions (e.g., FortiGuard AntiVirus service integrated into FortiGate, FortiMail, FortiClient, and FortiEDR).
- Implement application control to prevent unauthorized execution from temporary directories (`%TMP%`).
- Enforce principle of least privilege to restrict user rights, hindering the ransomware's ability to execute recovery disabling commands.
- Regularly back up data offline and ensure recovery mechanisms (VSS) are tested and functional before an infection attempt.
## Related Tools/Techniques
- Earlier variants of Chaos ransomware (written in .NET).
- General Ransomware TTPs involving volume shadow copy deletion.
- Clipboard hijacking techniques used by other malware families for cryptocurrency theft.