Winlock

Overview

Winlock (historically documented across threat intelligence platforms under designations including Ransom:Win32/Winlock, Trojan-Ransom.Win32.Winlock, and Win32/Winlock) represents a pioneering and destructive screen-locking ransomware family active since 2010. Distributed through compromised adult websites, malicious codec downloads, and drive-by download vectors, Winlock replaces or hooks the Windows graphical shell (explorer.exe), setting itself as the default shell under HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon. Upon execution, Winlock renders a non-dismissible, full-screen lockdown banner that covers the desktop, disables Task Manager, registry editing tools, and task switching keystrokes (Alt+Tab, Ctrl+Alt+Del). The locker displays fake legal notices or pornographic scareware messages demanding SMS premium rate messages or cryptocurrency payment to receive a dynamic unlock code.

Known aliases

Threat reports may refer to this family under multiple names:

• Ransom:Win32/Winlock
• Trojan-Ransom.Win32.Winlock
• Win32/Winlock
• Ransom.Winlock
• Ransom:Win32/Winlock.A

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_WINLOCK_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Winlock"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "winlock" ascii wide nocase
        $s2 = "ransom:win32/winlock" ascii wide nocase
        $s3 = "trojan-ransom.win32.winlock" ascii wide nocase
        $s4 = "win32/winlock" ascii wide nocase
        $s5 = "ransom.winlock" ascii wide nocase
        $s6 = "ransom:win32/winlock.a" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Winlock (Ransomware) Execution & Triage
id: eb0f0076-0c17-5a63-96dc-daaf2e2454ee
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Winlock 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/winlock
- 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.t1491_001
- attack.t1547_004
- attack.t1562_001
- attack.t1112
- attack.t1189
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_WINLOCK_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Winlock 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 = "winlock" 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. Reboot the affected system into Windows Recovery Environment (WinRE) or bootable offline media.
2. Load the offline SYSTEM and SOFTWARE registry hives using regedit.
3. Verify and restore HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon 'Shell' to 'explorer.exe'.
4. Delete the locker binary located in %APPDATA%, %TEMP%, or %WINDIR%.
5. Remove DisableTaskMgr and DisableRegistryTools policies under HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System.

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 SMS or cryptocurrency ransom demand, as codes provided are rarely functional.
2. Do not reformat the hard drive before attempting Winlogon shell restoration, as user files remain unencrypted.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - Ransom:Win32/Winlock
• Kaspersky Lab - Winlock Ransomware Historical Analysis
• Trend Micro Threat Encyclopedia - Ransom_Winlock
• Search "winlock" on VirusTotal (External Analysis)
• Search "winlock" on Any.Run (Sandbox Sandbox)
• Search "winlock" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Lockscreen
• Bagsu
• Oasisminus
• Prosti
• Dycler
• Lurk
• Antivirus
• Mongolock

Machine-readable

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