Crowti

Overview

Ransom:Win32/Crowti is Microsoft's internal detection designation for the infamous **CryptoWall** ransomware family. Emerging in the mid-2010s as a successor to CryptoLocker, CryptoWall (Crowti) was one of the most widespread and financially devastating ransomware strains in history. It pioneered the use of the Tor anonymity network for Command and Control (C2) and heavily refined the Ransomware-as-a-Service (RaaS) affiliate distribution model.

Understanding Crowti (CryptoWall Ransomware)
To an end-user, the impact is catastrophic: all personal documents, photos, and databases are suddenly inaccessible, appended with random extensions, and the desktop background is replaced with a ransom note demanding Bitcoin payment via a Tor hidden service. For a security team, a Crowti infection represents a severe breach, as the ransomware's robust RSA-2048 encryption (`T1486`) is mathematically impossible to break without the private key held by the attackers.

Execution and Encryption Mechanics
Crowti was distributed via massive malspam campaigns containing weaponized CHM (Compiled HTML Help) files (`T1566.001`), JavaScript droppers, or via exploit kits (like Angler or Nuclear) (`T1189`). Upon execution (`T1204.002`), it establishes persistence in the Registry (`T1547.001`) and aggressively deletes Volume Shadow Copies (`vssadmin.exe Delete Shadows /All /Quiet`) (`T1490`) to prevent easy recovery. It communicates with its C2 server via heavily obfuscated proxies (like I2P or Tor) (`T1090.003`) to receive its unique public encryption key, and then systematically encrypts user files across local drives and mapped network shares (`T1486`).

Indicators of Compromise & Impact
The impact is total data loss and severe business disruption. Host-based IoCs include EDR alerts for the execution of `vssadmin.exe`, massive bursts of file modification operations, the dropping of ransom notes (e.g., `HELP_DECRYPT.HTML`, `HELP_YOUR_FILES.TXT`), and the presence of the Crowti executable hiding in `%AppData%`. Network IoCs include DNS requests to known Tor gateways or I2P proxies.

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

Sigma Rule

title: Suspicious Crowti Activity
id: e242978e2cec1f7863e17e185dc6b189
status: experimental
description: Detects generic indicators of the crowti malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*crowti*"
    condition: selection
level: medium

Containment & Response Steps

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

1. IMMEDIATELY sever network connectivity to the infected endpoint to prevent Crowti from encrypting data on mapped corporate network shares.
2. Do not attempt to reboot the machine if the encryption process is still actively running, as this may corrupt partially encrypted files.
3. Identify the initial entry vector (e.g., the specific phishing email or malicious CHM file) and purge it from the corporate environment.
4. Restore the affected systems from secure, offline backups that were not accessible to the infected endpoint.

What to Avoid

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

1. Do not rely on Volume Shadow Copies for recovery, as Crowti's first action is to delete them.
2. Avoid paying the ransom unless absolutely critical for business survival, as it funds further cybercrime and there is no guarantee of receiving the decryptor.

References & External Analysis

• Search "crowti" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Genericrxeg
• Recex
• Scriptkd
• Launcher
• Slugin

Machine-readable

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