Locky

Overview

Locky is one of the most prolific, damaging, and aggressively distributed ransomware strains in cyber history, first emerging in February 2016. Associated with the Russian-speaking syndicate behind the Dridex banking trojan (Evil Corp) and distributed at unprecedented scale via the Necurs spam botnet, Locky compromised hundreds of thousands of corporate and public sector networks worldwide by bombarding global email gateways with tens of millions of malicious attachments daily. Locky gained international notoriety in February 2016 when an infection paralyzed the Hollywood Presbyterian Medical Center in Los Angeles, locking emergency room electronic health records, radiation therapy devices, and lab databases, forcing hospital staff to declare an internal disaster and revert to paper records for over a week. Locky utilized an embedded RSA-2048 public key to securely encapsulate a randomly generated local AES-128 key. Over its two-year operational lifecycle, Locky cycled through numerous iconic file extensions—including `.locky`, `.zepto`, `.odin`, `.thor`, `.aesir`, `.osiris`, `.diablo6`, and `.lukitus`—evading signature detection through constant crypter and transport mutations.

Known aliases

Threat reports may refer to this family under multiple names:

• Locky
• Ransom.Locky
• Win32/Locky
• Trojan-Ransom.Win32.Locky

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• Necurs / Dridex (Evil Corp) Cybercrime Syndicate High confidence
  Basis: Documented by US CISA, FBI, and Europol as distributed exclusively via the Necurs botnet and sharing loader and infrastructure affiliations with the Dridex (Evil Corp) cybercrime enterprise. [source]

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: Dridex Loader Ecosystem

Known Derivatives & Downstream Variants: Locky (.Locky) · Zepto (.Zepto) · Odin (.Odin) · Thor (.Thor) · Osiris (.Osiris) · Lukitus (.Lukitus) · Ykcol (.Ykcol)

MITRE ATT&CK Techniques

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

Tactical Mitigations

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

• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.
• T1566.001: Scan email attachments for malicious macros, scripts, or suspicious archive files.

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-2016-0189 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2017-0199 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Command & Control (C2) and Network Profile

How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.

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.

• 4a242f36f6d895f462ebc8375e87a26f8303f26cfb16954316d2ca0190abf0c1
• e236526eb8fb386f6f1c4e97669e4f5530ecdfce9a2ffb38ab8fa176df2c75a4

Delivery vectors

• Massive spam email blasts from the Necurs botnet containing obfuscated Microsoft Office macros or ZIP archives with VBScript/JS downloaders
• Exploit kits (Neutrino, RIG) weaponized with CVE-2016-0189

Persistence mechanisms

• Non-persistent execution: executes, scrambles local files and mapped network shares, changes desktop wallpaper, and self-deletes
• Deletes Windows Volume Shadow Copies using vssadmin.exe delete shadows /all /quiet

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_LOCKY_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Locky"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "locky" ascii wide nocase
        $s2 = "locky" ascii wide nocase
        $s3 = "ransom.locky" ascii wide nocase
        $s4 = "win32/locky" ascii wide nocase
        $s5 = "trojan-ransom.win32.locky" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Locky (Ransomware) Execution & Triage
id: 893380da-8517-584e-9573-b92ab78ba365
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Locky 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/locky
- 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.t1071_001
- attack.t1566_001
- attack.t1568_002
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_LOCKY_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Locky 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 = "locky" 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. Immediately isolate affected host(s) from the internal network (disconnect physical Ethernet and disable Wi-Fi/Bluetooth) to prevent Locky from spreading laterally or encrypting network-attached storage (NAS) and shared SMB volumes.
2. Preserve volatile system memory (RAM capture) on a representative endpoint before attempting a reboot or power-down, as Locky symmetric encryption keys or uncompiled payload components may still reside in memory.
3. Audit process execution logs and terminate active scripting interpreters (e.g. PowerShell, CMD, WScript) or commands executing 'vssadmin.exe delete shadows' or 'wbadmin' used by Locky to inhibit recovery.
4. Investigate the initial compromise vector (such as exposed RDP instances, spearphishing attachments, or vulnerable edge gateways) and enforce an immediate credential reset for all compromised Active Directory accounts.
5. Restore critical assets and databases exclusively from verified, air-gapped, or immutable offline backups once the Locky binary and related persistence hooks are eradicated.

What to Avoid

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

1. Do not restart or power cycle infected systems prematurely; doing so destroys volatile RAM encryption keys and may trigger bootloader locking logic embedded in Locky.
2. Avoid negotiating or paying the extortion demand without prior forensic evaluation and consultation with incident response specialists, as payment does not guarantee data recovery.
3. Do not connect clean backup drives or external storage to the affected network until Locky eradication is completely verified.

References & External Analysis

• CISA Advisory - Ransomware Deployment and Necurs Ecosystem
• US Department of Health and Human Services (HHS) - Locky Healthcare Impact
• MITRE ATT&CK - Locky
• Search "locky" on VirusTotal (External Analysis)
• Search "locky" on Any.Run (Sandbox Sandbox)
• Search "locky" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Xylauncher
• Ubibila
• Xiazai
• Flystudi
• Gimemo
• Olympicdestroyer
• Bluewushu
• Tikoog

Machine-readable

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