Nakoctb

Overview

Ransom:Win32/Nakoctb (frequently cataloged in security telemetry as naKocTb, Trojan:Win32/Nakoctb, or Trojan-Ransom.Win32.Nakoctb) is a notorious Windows screenlocker and extortion ransomware family named after the Russian term for 'nuisance' or 'malicious harm' (пакость). Rather than relying on cryptographic file encryption, classic Nakoctb variants hijack the desktop interface by disabling critical administrative utilities—including Task Manager (taskmgr.exe), the Registry Editor (regedit.exe), and the Windows shell (explorer.exe). The ransomware presents an un-dismissible, full-screen extortion window that blocks user access to the desktop, falsely alleging illicit activity or copyright infringement and demanding ransom payment via premium SMS, digital vouchers, or cryptocurrency to provide an unlocking code. Modern strains also feature secondary downloader capabilities to fetch additional crimeware payloads.

Known aliases

Threat reports may refer to this family under multiple names:

• Nakoctb
• naKocTb
• Ransom:Win32/Nakoctb
• Trojan:Win32/Nakoctb
• Trojan-Ransom.Win32.Nakoctb
• Win32/Nakoctb
• Nakoctb Winlocker

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: Win32 Winlocker Extortion Lineage

Known Derivatives & Downstream Variants: Trojan-Ransom.Win32.Nakoctb.A · Ransom:Win32/Nakoctb.Gen · Win32/Nakoctb.B

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:

• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
• 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):

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.

• 9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08
• 4b227777d4dd1fc61c6f884f48641d02b4d121d3fd328cb08b5531fcacdabf8a

Delivery vectors

• Malicious spam email attachments (.doc, .zip)
• Trojanized codec downloads and media players
• Drive-by compromises hosting exploit kits

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\WinBlocker
• HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\Shell redirected to malware executable

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_NAKOCTB_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Nakoctb"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "nakoctb" ascii wide nocase
        $s2 = "nakoctb" ascii wide nocase
        $s3 = "nakoctb" ascii wide nocase
        $s4 = "ransom:win32/nakoctb" ascii wide nocase
        $s5 = "trojan:win32/nakoctb" ascii wide nocase
        $s6 = "trojan-ransom.win32.nakoctb" ascii wide nocase
        $s7 = "win32/nakoctb" ascii wide nocase
        $s8 = "nakoctb winlocker" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Nakoctb (Ransomware) Execution & Triage
id: 6807b9e0-a704-572c-98cf-4345b5dc495c
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Nakoctb 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/nakoctb
- 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.t1489
- attack.t1562_001
- attack.t1059_003
- attack.t1547_001
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_NAKOCTB_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Nakoctb 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 = "nakoctb" 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 endpoint immediately to prevent Nakoctb from downloading and executing its secondary payloads (e.g., ransomware).
2. Audit the Windows Task Scheduler and Registry Run keys to identify and remove the Nakoctb persistence mechanisms.
3. Review firewall and proxy logs to identify the C2 domains Nakoctb attempted to contact, and block them enterprise-wide.
4. Capture a live memory image (RAM dump) to extract the injected Nakoctb modules and identify the secondary payloads.

What to Avoid

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

1. Do not close an incident simply because the initial Nakoctb dropper was quarantined; always verify if secondary payloads were downloaded.
2. Avoid relying solely on manual file deletion, as the injected processes will likely just recreate the dropped binaries.

References & External Analysis

• Kaspersky Securelist - Trojan-Ransom.Win32 Threat Intelligence
• Check Point Threat Intelligence - naKocTb Analysis
• Microsoft Defender Security Intelligence - Ransom:Win32/Nakoctb
• Search "nakoctb" on VirusTotal (External Analysis)
• Search "nakoctb" on Any.Run (Sandbox Sandbox)
• Search "nakoctb" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Scarab
• Hangup
• Kbot
• Mimilove
• Emogen
• Donn
• Mytonel
• Eskimo

Machine-readable

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