Brambul

Overview

Worm:Win32/Brambul is an aggressive network-spreading worm developed by North Korean state-sponsored threat group HIDDEN COBRA (Lazarus Group / APT38). Discovered in 2009 and detailed in US-CERT Alert TA18-053A, Brambul is engineered to scan local subnets and random external internet IP addresses across TCP port 445, aggressively brute-forcing Server Message Block (SMB) credentials using hardcoded administrative password lists. Upon successful authentication, Brambul copies its payload to the target machine via administrative network shares (ADMIN$ or C$), registers Windows Run keys to achieve persistence, and uses embedded SMTP routines to exfiltrate detailed victim system configuration data back to threat actor email drop boxes.

Known aliases

Threat reports may refer to this family under multiple names:

• Brambul
• Worm:Win32/Brambul
• Hidden Cobra Brambul
• W32/Brambul
• Trojan.Brambul
• Lazarus SMB Worm

Threat Actor Attribution

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

• HIDDEN COBRA (Lazarus Group / APT38) High confidence
  Basis:

Family Pedigree & Lineage

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

Known Derivatives & Downstream Variants: Brambul Smb Worm V1 · Brambul Hidden Cobra Build · Brambul Lazarus Reconnaissance Spreader

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:

• T1071.003: Monitor network traffic for anomalous application layer protocols like non-standard HTTP/S patterns or unexpected DNS requests.

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-2008-4250 — 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.

• 5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6e
• 7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f

Delivery vectors

• smb_port_445_brute_force
• lateral_network_transfer

Persistence mechanisms

• HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
• Windows System Directory Executable Drops

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_BRAMBUL_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Brambul"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "brambul" ascii wide nocase
        $s2 = "brambul" ascii wide nocase
        $s3 = "worm:win32/brambul" ascii wide nocase
        $s4 = "hidden cobra brambul" ascii wide nocase
        $s5 = "w32/brambul" ascii wide nocase
        $s6 = "trojan.brambul" ascii wide nocase
        $s7 = "lazarus smb worm" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Brambul (Worm) Execution & Triage
id: 504edb82-6600-5a3f-922e-838246d5c974
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Brambul malware family. Detects suspicious execution from temporary user
  directories with hidden window flags and background transfer utilities.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/brambul
- 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.worm
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1110_001
- attack.t1570
- attack.t1046
- attack.t1547_001
- attack.t1071_003
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \cmd.exe
    - \powershell.exe
    - \cscript.exe
    - \wscript.exe
    CommandLine|contains:
    - AppData\Local\Temp
    - -WindowStyle Hidden
    - /e:jscript
    - bitsadmin /transfer
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: medium

rule MALWARE_WIN_BRAMBUL_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Brambul 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 = "brambul" 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 endpoints exhibiting aggressive outbound TCP port 445 network scanning.
2. Enforce strict firewall rules blocking inbound and outbound SMB (port 445) at enterprise perimeter gateways.
3. Force a domain-wide password reset for any administrator accounts compromised during brute-force attempts.
4. Deploy network monitoring to alert on repeated failed SMB authentication events (Event ID 4625).

What to Avoid

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

1. Do not allow direct SMB port 445 exposure to the public internet under any circumstances.
2. Avoid using default, blank, or easily guessable passwords on local administrator accounts.
3. Never ignore high volumes of internal SMB authentication failures occurring across subnets.

References & External Analysis

• US-CERT / CISA Alert TA18-053A: HIDDEN COBRA - Brambul SMB Worm
• MITRE ATT&CK Group G0032: Lazarus Group (HIDDEN COBRA)
• NIST National Vulnerability Database CVE-2008-4250
• CISA Advisory: TA18-053A
• Search "brambul" on VirusTotal (External Analysis)
• Search "brambul" on Any.Run (Sandbox Sandbox)
• Search "brambul" 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: TA18-053A ↗

Frequently Asked Questions

Related Threats (Category: Worm)

Explore other documented threats in the same operational category:

• Sytro
• Mira
• Brontok
• Kolabc
• Ngrbot
• Blaster
• Sfone
• Mydoom

Machine-readable

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