Cryptxxx

Overview

Ransom:Win32/Cryptxxx (also known as UltraCrypter) is a highly destructive, multi-faceted malware family. Unlike simple ransomware that only encrypts files, Cryptxxx acts as a dual-threat: it operates as a severe information stealer (`T1552`) to harvest Bitcoin wallets and passwords *before* it begins its cryptographic attack (`T1486`). This ensures the attackers can monetize the infection even if the victim refuses to pay the ransom.

Understanding Cryptxxx (Dual-Threat Ransomware)
To an end-user, the impact is catastrophic: personal files are locked with a `.crypt` or `.crypz` extension, a ransom note demands payment, and they may later find their cryptocurrency wallets drained. For a SOC analyst, Cryptxxx represents a massive breach of confidentiality and availability. It was heavily distributed by the Angler and Neutrino Exploit Kits.

Execution and Extortion Mechanics
Upon execution, Cryptxxx first establishes persistence (often copying itself to `%AppData%` and modifying the `Run` registry key). Before encrypting anything, it scans the hard drive for Bitcoin wallet files (`wallet.dat`), FTP credentials, email passwords, and browser cookies, exfiltrating this data to its C2 server (`T1041`). Once exfiltration is complete, it begins a rapid encryption routine using RSA-4096 and AES-256 (`T1486`). It actively attempts to delete Volume Shadow Copies (`T1490`) using `vssadmin.exe` to thwart recovery efforts.

Indicators of Compromise & Impact
The impact is total data loss and severe credential compromise. Host-based IoCs include the presence of files appended with `.crypt`, `.crypz`, or `.crypt1`. Ransom notes are typically dropped as `de_crypt_readme.txt` or `de_crypt_readme.html`. EDR tools will flag the execution of `vssadmin.exe delete shadows /all /quiet`. Network IoCs include initial exfiltration traffic (often over non-standard ports) followed by Tor-based C2 communication.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

Tiered Detection Rules (Cisco CAIRN Model)

Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:

rule MALWARE_WIN_CRYPTXXX_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Cryptxxx"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "cryptxxx" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Cryptxxx (Ransomware) Execution & Triage
id: d3f7e3ad-eec9-5dc0-9c92-50a52dae4594
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Cryptxxx malware family. Detects volume shadow copy deletion, boot status
  tampering, and recovery inhibition characteristic of modern ransomware operations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/cryptxxx
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.ransomware
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1486
- attack.t1490
- attack.t1552
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \vssadmin.exe
    - \wmic.exe
    - \wbadmin.exe
    - \bcdedit.exe
    CommandLine|contains:
    - delete shadows
    - shadowcopy delete
    - resize shadowstorage
    - recoveryenabled no
    - ignoreallfailures
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: critical

rule MALWARE_WIN_CRYPTXXX_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Cryptxxx tradecraft"
        tier = "T3 - Attribution Fingerprint"
        confidence = "High (Confirmed Family Signature)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        // Core family identifier & heuristic payload signatures
        $attrib_str = "cryptxxx" ascii wide nocase
        $pe_magic = "MZ" ascii
        $net_marker = "http" ascii nocase
    condition:
        uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}

Containment & Response Steps

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

1. Isolate the infected endpoint IMMEDIATELY by physically disconnecting the network cable to halt the exfiltration of credentials and the encryption of network shares.
2. Assume all passwords and cryptocurrency wallets stored on the machine are compromised; force immediate password resets from a clean machine.
3. Check NoMoreRansom.org; flaws in earlier versions of Cryptxxx allowed security researchers to release free decryption tools.
4. Restore the encrypted files from an offline, secure backup.

What to Avoid

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

1. Do not pay the ransom; paying funds criminal enterprises, and free decryptors exist for many variants of Cryptxxx.
2. Do not assume that removing the ransomware solves the problem; you must address the stolen credentials.

References & External Analysis

• Search "cryptxxx" on VirusTotal (External Analysis)
• Search "cryptxxx" on Any.Run (Sandbox Sandbox)
• Search "cryptxxx" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Jnkfasgyvyo
• Recory
• Epack
• Armadillo
• Chistudi
• Jottix
• Xyligan
• Magnat

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/cryptxxx.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.