Cryptomix

Overview

Ransomware:Win32/Cryptomix is a well-known, historically significant ransomware family. Its primary objective is to encrypt the victim's files using strong cryptographic algorithms (typically RSA-2048 and AES-256) (`T1486`) and extort cryptocurrency. Cryptomix is notable for its numerous variants (like Cryptoshield), its shifting network of payment portals hosted on the Tor network, and its aggressive deletion of system recovery options.

Understanding Cryptomix (Ransomware)
To an end-user, a Cryptomix infection is devastating. They will suddenly find their documents, photos, and databases inaccessible, appended with an extension (which varied heavily between versions, e.g., `.scl`, `.code`, `.rmp`), accompanied by a stark 'Ransom Note' providing instructions to pay the attackers via Bitcoin. For an organization, it represents a critical incident requiring immediate network isolation.

Execution and Encryption Mechanics
Cryptomix was typically delivered via exploit kits (like RIG or GrandSoft) or via malicious spam attachments. Upon execution, it immediately executes commands to delete Volume Shadow Copies (`vssadmin.exe delete shadows`) (`T1490`) and disable the Windows Startup Repair feature to prevent easy data recovery. It then rapidly traverses local drives and mapped network shares (`T1012`), encrypting files. A unique feature of early Cryptomix was its reliance on a hardcoded list of public keys; if it couldn't reach its C2 server, it would use an 'offline' key, which security researchers were sometimes able to extract to build free decryptors.

Indicators of Compromise & Impact
The impact is the total loss of data availability. Host-based IoCs include the sudden renaming of thousands of files, the presence of ransom notes (e.g., `HELP_INSTRUCTION.txt`), and EDR alerts for rapid file modification operations. System logs will show the execution of commands designed to inhibit system recovery (`vssadmin`, `bcdedit`). Network IoCs include DNS requests to known Cryptomix C2 infrastructure, often routing through compromised websites.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the MITRE ATT&CK framework:

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_CRYPTOMIX {
    meta:
        description = "Detects Cryptomix (ransomware)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "cryptomix" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Cryptomix Activity
id: c9e3aa30ac34cfce7a61a7c8a49cd7ed
status: experimental
description: Detects generic indicators of the cryptomix malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*cryptomix*"
    condition: selection
level: medium

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Isolate the infected machine from the network immediately to stop the encryption process from spreading to mapped network shares.
2. Do not reboot the machine; if the encryption process is active, rebooting may finalize the damage or destroy volatile memory keys.
3. Check resources like 'No More Ransom' to see if a free decryptor exists for the specific variant of Cryptomix you are facing.
4. Restore operations from known-good, offline backups; paying the ransom is highly discouraged and funds criminal enterprises.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not connect backup drives to the infected machine until it has been completely wiped and reimaged.
2. Avoid paying the ransom unless absolutely critical for human safety, as Cryptomix operators were known for poor customer service and failing to deliver decryptors.

References & External Analysis

• Search "cryptomix" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Bhxu
• 000C
• P2Pworm
• Zero
• Corrempa

Machine-readable

Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/api/cryptomix.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.