Lockscreen

Overview

Ransomware:Win32/Lockscreen is a heuristic detection for a specific, older class of ransomware known as 'Screen Lockers'. Unlike modern crypto-ransomware that actually encrypts files, Lockscreen variants simply deny access to the Windows graphical user interface, displaying a persistent, full-screen ransom demand (often masquerading as law enforcement).

Understanding Lockscreen
To the victim, the effect is immediate and terrifying: their computer is completely locked down. The screen displays a message claiming the FBI or local police have detected illegal activity (e.g., piracy) and demands a 'fine' paid via Ukash, Paysafecard, or Bitcoin. For security analysts, Lockscreen malware is considered less sophisticated than crypto-ransomware. The underlying data on the hard drive remains unencrypted and perfectly intact; the malware merely prevents the user from accessing it by hijacking the Windows shell or exploiting boot mechanisms.

Execution and Lockdown Mechanics
Lockscreen variants (like Reveton) are typically distributed via exploit kits (`T1189`) or drive-by downloads. Upon execution, the malware modifies critical Registry keys. Most commonly, it changes the `Shell` value in `HKCU\Software\Microsoft\Windows NT\CurrentVersion\Winlogon` from `explorer.exe` to the malware's executable (`T1547.004`). When the user logs in, the malware launches instead of the Windows desktop, displaying the lock screen. Advanced variants may also disable Task Manager, Safe Mode, and Command Prompt to prevent the user from bypassing the screen.

Indicators of Compromise & Impact
The impact is immediate loss of availability, but without data destruction. EDR platforms should alert on unauthorized modifications to the Winlogon registry keys. Because the system is locked, incident response often requires booting from a Live USB or utilizing a recovery environment to access the registry offline and repair the modified `Shell` value.

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

Sigma Rule

title: Suspicious Lockscreen Activity
id: 9f2f4e1b83dd692d4d41ff492c240a77
status: experimental
description: Detects generic indicators of the lockscreen malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*lockscreen*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Do not pay the ransom; the files are not encrypted, and the 'police' warning is entirely fraudulent.
2. Boot the infected machine into 'Safe Mode with Command Prompt' (if the malware has not disabled it) to bypass the graphical lock screen.
3. Utilize a Live OS (like a Linux USB or Windows PE) to mount the hard drive offline, load the Windows Registry hive, and manually restore the `Winlogon\Shell` key to `explorer.exe`.
4. Once the Windows shell is restored, run a comprehensive antivirus scan to remove the underlying malware binaries.

What to Avoid

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

1. Avoid assuming the data is lost; Lockscreen malware rarely encrypts files. Do not format the hard drive without attempting a registry repair first.
2. Do not attempt to interact with the lock screen interface or click any links it provides.

References & External Analysis

• Search "lockscreen" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: ransomware)

Explore other malware families in the same category:

• Filefinder
• Virgilio
• Smee
• Stegvob
• Yolov

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/api/lockscreen.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.