Ryuk

Overview

Ryuk is one of the most destructive and lucrative enterprise ransomware families in cybersecurity history, first identified in August 2018 and operated by the Russian cybercriminal syndicate Wizard Spider (tracked by threat analysts as UNC1878 and TEMP.MixMaster). Derived directly from the Hermes ransomware codebase originally attributed to the Lazarus Group, Ryuk pioneered the targeted 'big game hunting' methodology against high-value commercial targets, local municipalities, and healthcare networks. Rather than deploying via indiscriminate spray-and-pray spam, Ryuk was deployed as the devastating final payload of complex multi-stage intrusion campaigns initiated by TrickBot, Emotet, or BazarLoader. Once initial network access was secured, operators conducted extensive Active Directory reconnaissance using BloodHound and AdFind, escalated privileges to Domain Admin using Zerologon (CVE-2020-1472), and mapped enterprise network shares. In a devastating technical innovation, Ryuk operators weaponized Wake-on-LAN (WOL) magic packets across local subnets to wake powered-down corporate workstations and servers before triggering encryption. Ryuk executes a multi-threaded hybrid encryption routine pairing ChaCha20 symmetric stream ciphers with RSA-4096 asymmetric public keys, appending the '.RYK' extension to targeted files. Prior to encryption, the malware terminates over 40 security and backup services using net stop, kills 150+ database and system processes via taskkill, and systematically deletes Volume Shadow Copies using vssadmin.exe delete shadows /all /quiet and bcdedit.exe to prevent system restore. CISA released Alert AA20-302A warning of widespread Ryuk ransomware attacks targeting the U.S. healthcare and public health sector.

Known aliases

Threat reports may refer to this family under multiple names:

• Ryuk Ransomware
• Trojan.Ransom.Ryuk
• Win32/Ryuk
• Ransom.Ryuk
• Hermes-Ryuk

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Derived From / Upstream Ancestry: Hermes

Known Derivatives & Downstream Variants: Ryuk_V1 · Ryuk_V2 · Ryuk_Wakeonlan · Conti_Precursor

MITRE ATT&CK Techniques

This family has been observed using the following ATT&CK techniques: T1486 · T1490 · T1021.002 · T1059.001 · T1068 · T1003.001 · T1071.001 · T1547.001

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1003.001: Monitor for LSASS memory dumping or registry SAM extraction. Enable Credential Guard on Windows systems.
• T1059.001: Restrict execution of PowerShell. Enforce PowerShell Constrained Language Mode and Script Block Logging.
• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.

MITRE D3FEND™ Defensive Countermeasures

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

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2020-1472 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• 2b6a5db21d00f7e44a42e5d7db69b466ea2084c55bc66c5d1e2e1329c31b312b
• 5c84dfc8df34e64ff476bf43a8ce90150e7b95204481ae515efb64dd9bf0e20e
• a17387f5df2307ef086915091219b671a172776c59b67195721118182969b761

Delivery vectors

• Staged via TrickBot, BazarLoader, and Emotet loaders following corporate network infiltration
• Spear-phishing emails containing malicious macros or weaponized ISO containers
• Exploitation of Active Directory Zerologon flaw CVE-2020-1472 for instant domain compromise

Persistence mechanisms

• Creation of service entries with randomized names in Windows Service Control Manager
• HKLM\Software\Microsoft\Windows\CurrentVersion\Run entry pointing to ryuk executable in %PUBLIC%
• Scheduled task configured to launch ryuk binary across all domain-joined endpoints

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_RYUK_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Ryuk"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "ryuk" ascii wide nocase
        $s2 = "ryuk ransomware" ascii wide nocase
        $s3 = "trojan.ransom.ryuk" ascii wide nocase
        $s4 = "win32/ryuk" ascii wide nocase
        $s5 = "ransom.ryuk" ascii wide nocase
        $s6 = "hermes-ryuk" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Ryuk (Ransomware) Execution & Triage
id: 9993c81f-9249-50f5-bf7e-46e5eed6ead1
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Ryuk 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/ryuk
- 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.t1021_002
- attack.t1059_001
- attack.t1068
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_RYUK_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Ryuk 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 = "ryuk" 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
}

References & External Analysis

• CISA Joint Advisory AA20-302A: Ransomware Activity Targeting Healthcare and Public Health Sector
• Mandiant: UNC1878 Wizard Spider Ryuk Intrusion Campaigns
• CrowdStrike: Wizard Spider Threat Profile and Ryuk Analysis
• Check Point Research: Ryuk Ransomware Deep Dive
• CISA Advisory: AA20-302A
• Search "ryuk" on VirusTotal (External Analysis)
• Search "ryuk" on Any.Run (Sandbox Sandbox)
• Search "ryuk" on MalwareBazaar (Malware Samples)

North American Authority Advisory (CISA / NIST)

The Cybersecurity and Infrastructure Security Agency (CISA) has published an official US federal advisory on this family, which can be mapped to NIST Cybersecurity Framework (CSF) incident response controls: AA20-302A ↗

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Exdek
• Spnr
• Nion
• Zenfly
• Nsanti
• Genericrxdc
• Psexec
• Betload

Machine-readable

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