Cryptojoker
Overview
Executive Summary
CryptoJoker is a highly destructive strain of file-encrypting Ransomware. It is designed to quickly infiltrate a system, encrypt all valuable user data (documents, databases, images) using strong cryptographic algorithms, and demand a cryptocurrency payment (usually Bitcoin) in exchange for the decryption key. It poses an immediate, catastrophic threat to business continuity and data availability.Infection Vector and Technical Capabilities
CryptoJoker is typically distributed through massive, automated malspam campaigns containing malicious attachments, via drive-by downloads from compromised websites (Exploit Kits), or directly deployed by attackers who have purchased access to the network from Initial Access Brokers (often via compromised RDP endpoints). Upon execution, CryptoJoker performs a rapid, highly visible attack:- VSS Deletion and Backup Destruction: The ransomware's first action is to execute commands (e.g., `vssadmin.exe Delete Shadows /All /Quiet`) to delete Volume Shadow Copies and disable Windows Recovery, preventing the user from easily restoring the encrypted files.
- Rapid Encryption: It scans local drives and mapped network shares for specific file extensions. It typically uses a combination of AES for fast file encryption and RSA to secure the AES keys. Encrypted files are often appended with a specific extension (e.g., `.joker` or `.crpt`).
- Extortion and Ransom Note: Once encryption is complete, the malware drops a ransom note (usually a `.txt` or `.html` file) in every affected directory and changes the desktop wallpaper. The note provides instructions on how to access a Tor-hosted payment portal to purchase the decryption tool.
Threat Assessment
A CryptoJoker infection is a critical, tier-one security incident. It results in an immediate loss of data availability and severe operational disruption. Furthermore, many modern ransomware operations employ "double extortion," meaning they exfiltrate sensitive data *before* encrypting the network, threatening to leak it publicly if the ransom is not paid.Incident Response and Remediation
- Immediate Network Severance: The absolute highest priority is to physically sever the infected endpoint (and any servers it can reach) from the network to halt the spread of the encryption across mapped drives and prevent data exfiltration.
- DO NOT REBOOT: Do not reboot the infected machine. Rebooting can trigger "wiper" routines in some ransomware variants or clear volatile memory (RAM) that might contain the encryption key.
- Restore from Offline Backups: Paying the ransom is strongly discouraged, as it funds criminal enterprises and does not guarantee data recovery. Eradication requires a complete bare-metal wipe of the infected infrastructure and a full restoration from secure, offline (air-gapped) backups.
Known aliases
Threat reports may refer to this family under multiple names:
MITRE ATT&CK Techniques
This family has been observed using the following ATT&CK techniques: T1486 T1490 T1012
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_CRYPTOJOKER {
meta:
description = "Detects Cryptojoker (ransomware)"
author = "SystemHelpdesk Boilerplate Generator"
date = "2026-07-06"
strings:
$s1 = "cryptojoker" ascii wide nocase
$s2 = "ransom.cryptojoker" ascii wide nocase
$s3 = "trojan-ransom.win32.cryptojoker" ascii wide nocase
$s4 = "win32/filecoder.cryptojoker" ascii wide nocase
condition:
uint16(0) == 0x5a4d and any of them
}Sigma Rule
title: Suspicious Cryptojoker Activity
id: 397cd5bd7a9e3b6dad84b1bf569aac9e
status: experimental
description: Detects generic indicators of the cryptojoker malware family.
logsource:
category: process_creation
product: windows
detection:
selection:
Image|endswith:
- '\cmd.exe'
- '\powershell.exe'
CommandLine|contains:
- "*cryptojoker*"
- "*ransom.cryptojoker*"
- "*trojan-ransom.win32.cryptojoker*"
- "*win32/filecoder.cryptojoker*"
condition: selection
level: mediumReferences & External Analysis
- Search "cryptojoker" on VirusTotal (External Analysis)
Frequently Asked Questions
How do I remove the Cryptojoker Ransomware from Windows?
Manual removal of Cryptojoker is highly discouraged as it may leave persistence mechanisms intact. We recommend disconnecting the device from the internet and utilizing a professional incident response service or enterprise-grade EDR software to conduct a full forensic sweep.
Is Cryptojoker a virus or a Ransomware?
Cryptojoker is classified as a Ransomware. Unlike traditional viruses that infect files, modern malware like Cryptojoker typically operates as a standalone payload designed to compromise systems, steal data, or deploy secondary stage implants.
What are the main symptoms of a Cryptojoker infection?
Symptoms of Cryptojoker can include unexpected system slowness, unauthorized outbound network traffic to unknown IP addresses, disabled security software, and suspicious background processes running from AppData or Temp directories.
Related Families (Category: ransomware)
Explore other malware families in the same category:
Protect Your Network Against Ransomwares
Want to prevent Cryptojoker and similar threats from compromising your organization? Read our comprehensive defensive guide: Ransomware Protection Guide.
Machine-readable
Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/api/cryptojoker.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.