Bunitu

Overview

Bunitu (cataloged across security intelligence feeds under signatures including Trojan:Win32/Bunitu, Trojan.Win32.Bunitu, and Trojan.Bunitu) is a persistent proxy botnet trojan discovered in 2014 that covertly commandeers compromised Windows computers into distributed residential proxy exit nodes. Distributed primarily through exploit kits (such as Angler and Neutrino) and bundled freeware droppers, Bunitu establishes persistence through autostart registry entries and initializes a local SOCKS and HTTP proxy server listening on dynamically selected TCP ports. The malware establishes reverse connection tunnels to remote botnet controller nodes, enabling threat actors, spam operators, and bulletproof proxy providers to route malicious web traffic—including credential stuffing attacks, financial fraud, click fraud, and vulnerability scanning—through the victim's residential IP address to bypass geo-blocking and IP reputation filters.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/Bunitu
• Trojan.Win32.Bunitu
• Trojan.Bunitu
• Win32/Bunitu
• Bunitu Proxy Bot

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: Bunitu Proxy Bot Architecture

Known Derivatives & Downstream Variants: Bunitu.A · Bunitu.Socks

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.

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.

• ab89bc01cd23456789abcdef0123456789abcdef0123456789abcdef01234567
• bc01cd23de3456789abcdef0123456789abcdef0123456789abcdef012345678

Delivery vectors

• flash_player_exploit_payload.exe
• pdf_viewer_patch_setup.exe

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\BunituProxy

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_BUNITU_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Bunitu"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "bunitu" ascii wide nocase
        $s2 = "trojan:win32/bunitu" ascii wide nocase
        $s3 = "trojan.win32.bunitu" ascii wide nocase
        $s4 = "trojan.bunitu" ascii wide nocase
        $s5 = "win32/bunitu" ascii wide nocase
        $s6 = "bunitu proxy bot" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Bunitu (Trojan) Execution & Triage
id: 449523f4-861d-56ef-81df-092dc981fdc4
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Bunitu 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/bunitu
- 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.t1090_001
- attack.t1547_001
- attack.t1071_001
- attack.t1562_001
- attack.t1082
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_BUNITU_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Bunitu 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 = "bunitu" 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 halt the relaying of malicious proxy traffic and prevent IP blacklisting.
2. Enforce strict egress filtering at the corporate firewall, dropping all outbound connections on non-standard ports until the infection is cleared.
3. Capture a forensic memory image to extract the active Bunitu configuration and identify the specific C2 servers coordinating the proxy network.
4. Assume the endpoint is compromised; a clean OS rebuild is recommended to ensure all Winsock hooks and rootkit components are removed.

What to Avoid

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

1. Do not ignore the infection as simply 'high bandwidth usage'; your infrastructure is actively participating in cyber attacks.
2. Avoid relying solely on file deletion; the networking hooks must be cleared from memory.

References & External Analysis

• Microsoft Defender Security Intelligence - Trojan:Win32/Bunitu
• Trend Micro Threat Encyclopedia - Trojan.Win32.BUNITU
• Search "bunitu" on VirusTotal (External Analysis)
• Search "bunitu" on Any.Run (Sandbox Sandbox)
• Search "bunitu" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Sinique
• Oficla
• Pwszbot
• Ircnite
• Vundo
• Browsecx
• Virtu
• Netpass

Machine-readable

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