Bzub

Overview

Bzub (classified in antivirus detection telemetry under designations including Trojan:Win32/Bzub, Trojan.Win32.Bzub, and Win32/Bzub) is a multi-stage trojan engineered to disguise itself as legitimate software, execute unauthorized commands, and coordinate with external command-and-control infrastructure. Disseminated across enterprise networks and consumer workstations via social engineering, phishing attachments, malicious drive-by downloads, or weaponized software cracks, Bzub executes an initial reconnaissance phase upon system ingress. The binary evaluates host privileges, detects active hypervisors and sandbox environments to evade behavioral analysis, and establishes resilient autostart persistence by configuring registry keys under HKCU\Software\Microsoft\Windows\CurrentVersion\Run or registering background Windows services. Operational mechanics characteristic of this family include deceptive executable masquerading, registry run key autostart, system telemetry gathering, and remote C2 beaconing. Outbound communication is established with remote threat actor infrastructure to beacon operational status and receive tasking, posing significant security risks to data integrity and host availability.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/Bzub
• Trojan.Win32.Bzub
• Win32/Bzub

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:

• T1185: Enforce strong MFA and use browser isolation or hardened browsers for sensitive financial or administrative portals to defeat session hijacking.

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_BZUB_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Bzub"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "bzub" ascii wide nocase
        $s2 = "trojan:win32/bzub" ascii wide nocase
        $s3 = "trojan.win32.bzub" ascii wide nocase
        $s4 = "win32/bzub" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Bzub (Trojan) Execution & Triage
id: eb6a211e-2115-58c2-897c-2c1809863d17
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Bzub 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/bzub
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1059_003
- attack.t1027
- attack.t1547_001
- attack.t1071_001
- attack.t1105
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_BZUB_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Bzub 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 = "bzub" 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 the endpoint from the network to sever the C2 connection and prevent the attacker from initiating fraudulent transactions.
2. Contact the victim's financial institutions immediately to freeze accounts and alert them to the high probability of a Man-in-the-Browser compromise.
3. Assume all web credentials stored on or entered into the machine have been stolen, and mandate enterprise-wide password resets.
4. Perform a complete wipe and reimage of the infected machine; banking trojans deeply hook into the OS and cannot be reliably removed by AV alone.

What to Avoid

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

1. Do not rely on standard MFA (like SMS codes) to protect accounts if a banking trojan is suspected, as the attacker is actively intercepting those codes via social engineering.
2. Avoid allowing the user to log into any sensitive accounts from the compromised machine, even after an AV scan claims it is clean.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - Trojan:Win32/Bzub
• Kaspersky Threat Intelligence - Trojan.Win32.Bzub
• MITRE ATT&CK - Enterprise Techniques
• Search "bzub" on VirusTotal (External Analysis)
• Search "bzub" on Any.Run (Sandbox Sandbox)
• Search "bzub" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Peepviewer
• Potao
• Plinch
• Bitrep
• Mailspy
• Midie
• Tear
• Travnet

Machine-readable

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